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UV tests

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  • Barry Chambers
    Evening All Over the past week, Gordon G0EWN and I have been doing some tests using UV radiation. This evening, we managed a 10km one-way contact from G8AGN/P
    Message 1 of 14 , Aug 11, 2012
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      Evening All

      Over the past week, Gordon G0EWN and I have been doing some tests using
      UV radiation. This evening, we managed a 10km one-way contact from
      G8AGN/P (Roper Hill, Sheffield) to G0EWN/P (Skew Hill, Sheffield).
      Gordon gave me a report of 569 even though the sky was not fully dark by
      21.30. Visibility across our usual test path was poor and the UV
      transmitter was not visible from the receive end.

      Equipment details are as follows:

      Tx
      --

      20 mw(dc input) UV LED (Maplin), measured output around 391nm (nominally
      400nm). The LED was CW keyed with a 976Hz tone using a PIC keyer.
      Transmitter antenna was a A4 Fresnel lens.

      Rx
      --
      Standard Bernie kit baseband Rx with a A4 Fresnel lens antenna.

      No scintillation was noticed on the received signal which continued to
      become stronger during the period of the test (21.00 - 21.30)


      --

      73
      Barry, G8AGN
    • d29602960
      Hi Barry, Congratulations on you recent success with UV LED s. Do you think the UV part of the spectrum offers any advantages in through-the-air optical comms
      Message 2 of 14 , Aug 12, 2012
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        Hi Barry,

        Congratulations on you recent success with UV LED's.

        Do you think the UV part of the spectrum offers any advantages in through-the-air optical comms over red or green wavelengths?

        Regards,

        Des (M0AYF)

        --- In UKNanowaves@yahoogroups.com, Barry Chambers <b.chambers@...> wrote:
        >
        > Evening All
        >
        > Over the past week, Gordon G0EWN and I have been doing some tests using
        > UV radiation. This evening, we managed a 10km one-way contact from
        > G8AGN/P (Roper Hill, Sheffield) to G0EWN/P (Skew Hill, Sheffield).
        > Gordon gave me a report of 569 even though the sky was not fully dark by
        > 21.30. Visibility across our usual test path was poor and the UV
        > transmitter was not visible from the receive end.
        >
        > Equipment details are as follows:
        >
        > Tx
        > --
        >
        > 20 mw(dc input) UV LED (Maplin), measured output around 391nm (nominally
        > 400nm). The LED was CW keyed with a 976Hz tone using a PIC keyer.
        > Transmitter antenna was a A4 Fresnel lens.
        >
        > Rx
        > --
        > Standard Bernie kit baseband Rx with a A4 Fresnel lens antenna.
        >
        > No scintillation was noticed on the received signal which continued to
        > become stronger during the period of the test (21.00 - 21.30)
        >
        >
        > --
        >
        > 73
        > Barry, G8AGN
        >
      • Gordon Fiander
        Hi Des, Barry is out today---regarding advantages of one part of the spectrum versus another ---visible red is probably the easiest frequency to work
        Message 3 of 14 , Aug 12, 2012
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          Hi Des,

          Barry is out today---regarding advantages of one part of the spectrum versus another ---visible red is probably the easiest frequency to work with---red propagates well through the atmosphere and photo diode based receivers are still reasonably efficient at 630nm. IR frequencies around 850nm look promising and  photo diodes have peak response / efficiency at IR. However, you need to be very careful with higher power devices---eye damage. UV is perhaps one of the most challenging nanowave frequencies---UV is to red light what 24ghz is to HF. Photo diode response at UV is quite low and UV LEDs are qrp devices----one would need to take care with any higher power devices as at IR, At the moment we are just testing what is possible. Last night, nothing was visible at all of the UV source---we used a low power red LED for aiming/ sighting. Barry modulated the red source with JT4---something we tested a few months ago---and had a keyed tone on the UV. Once I pointed my RX at the red source I could hear both the JT4 tones and Barry's cw indent---the red light was then turned out, leaving the (invisible at my end) UV source.
          I suppose an advantage of UV is that the police get fewer reports of UFO's (Joking).
          Bernie's Finningley TCVR is a very good RX---on a par with Clint's design for baseband RX at all nanowave frequencies---it isn't just for nanowave novices,

          Best wishes


          To: UKNanowaves@yahoogroups.com
          From: d29602960@...
          Date: Sun, 12 Aug 2012 12:32:27 +0000
          Subject: [UKNanowaves] Re: UV tests

           
          Hi Barry,

          Congratulations on you recent success with UV LED's.

          Do you think the UV part of the spectrum offers any advantages in through-the-air optical comms over red or green wavelengths?

          Regards,

          Des (M0AYF)

          --- In UKNanowaves@yahoogroups.com, Barry Chambers <b.chambers@...> wrote:
          >
          > Evening All
          >
          > Over the past week, Gordon G0EWN and I have been doing some tests using
          > UV radiation. This evening, we managed a 10km one-way contact from
          > G8AGN/P (Roper Hill, Sheffield) to G0EWN/P (Skew Hill, Sheffield).
          > Gordon gave me a report of 569 even though the sky was not fully dark by
          > 21.30. Visibility across our usual test path was poor and the UV
          > transmitter was not visible from the receive end.
          >
          > Equipment details are as follows:
          >
          > Tx
          > --
          >
          > 20 mw(dc input) UV LED (Maplin), measured output around 391nm (nominally
          > 400nm). The LED was CW keyed with a 976Hz tone using a PIC keyer.
          > Transmitter antenna was a A4 Fresnel lens.
          >
          > Rx
          > --
          > Standard Bernie kit baseband Rx with a A4 Fresnel lens antenna.
          >
          > No scintillation was noticed on the received signal which continued to
          > become stronger during the period of the test (21.00 - 21.30)
          >
          >
          > --
          >
          > 73
          > Barry, G8AGN
          >


        • Russ Stewart
          ... Hi guys and of course congratulations on the latest UV tests. As with most parts of the spectrum there are advantages and disadvantages. * Mie scattering
          Message 4 of 14 , Aug 12, 2012
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            On 12/08/2012 15:01, Gordon Fiander wrote:
             

            Hi Des,

            Barry is out today---regarding advantages of one part of the spectrum versus another ---visible red is probably the easiest frequency to work with---red propagates well through the atmosphere and photo diode based receivers are still reasonably efficient at 630nm. IR frequencies around 850nm look promising and  photo diodes have peak response / efficiency at IR. However, you need to be very careful with higher power devices---eye damage. UV is perhaps one of the most challenging nanowave frequencies---UV is to red light what 24ghz is to HF. Photo diode response at UV is quite low and UV LEDs are qrp devices----one would need to take care with any higher power devices as at IR, At the moment we are just testing what is possible. Last night, nothing was visible at all of the UV source---we used a low power red LED for aiming/ sighting. Barry modulated the red source with JT4---something we tested a few months ago---and had a keyed tone on the UV. Once I pointed my RX at the red source I could hear both the JT4 tones and Barry's cw indent---the red light was then turned out, leaving the (invisible at my end) UV source.
            I suppose an advantage of UV is that the police get fewer reports of UFO's (Joking).
            Bernie's Finningley TCVR is a very good RX---on a par with Clint's design for baseband RX at all nanowave frequencies---it isn't just for nanowave novices,

            Best wishes


            To: UKNanowaves@yahoogroups.com
            From: d29602960@...
            Date: Sun, 12 Aug 2012 12:32:27 +0000
            Subject: [UKNanowaves] Re: UV tests

             
            Hi Barry,

            Congratulations on you recent success with UV LED's.

            Do you think the UV part of the spectrum offers any advantages in through-the-air optical comms over red or green wavelengths?

            Regards,

            Des (M0AYF)

            --- In UKNanowaves@yahoogroups.com, Barry Chambers <b.chambers@...> wrote:
            >
            > Evening All
            >
            > Over the past week, Gordon G0EWN and I have been doing some tests using
            > UV radiation. This evening, we managed a 10km one-way contact from
            > G8AGN/P (Roper Hill, Sheffield) to G0EWN/P (Skew Hill, Sheffield).
            > Gordon gave me a report of 569 even though the sky was not fully dark by
            > 21.30. Visibility across our usual test path was poor and the UV
            > transmitter was not visible from the receive end.
            >
            > Equipment details are as follows:
            >
            > Tx
            > --
            >
            > 20 mw(dc input) UV LED (Maplin), measured output around 391nm (nominally
            > 400nm). The LED was CW keyed with a 976Hz tone using a PIC keyer.
            > Transmitter antenna was a A4 Fresnel lens.
            >
            > Rx
            > --
            > Standard Bernie kit baseband Rx with a A4 Fresnel lens antenna.
            >
            > No scintillation was noticed on the received signal which continued to
            > become stronger during the period of the test (21.00 - 21.30)
            >
            >
            > --
            >
            > 73
            > Barry, G8AGN
            >


            Hi guys and of course congratulations on the latest UV tests. As with most parts of the spectrum there are advantages and disadvantages.

            • Mie scattering becomes significantly better @ 400nM or there abouts when compared to 630nM and IR. Thus for qso's around corners 400nM is an advantage. <http://www.philiplaven.com/mieplot.htm>
            • At ~ 400nM there is a weak eye response as well as a poorer performance from our regular silicon photodetectors. There are very sensitive instrument detectors available but they tend to be costly.
            • There are 50W 400 nM LED arrays available on EBAY from time to time. I think these are for aquarium illumination. They are safe in this application as any short wavelength stuff will be filtered out by water molecules. I would like to see the emission spectrum before using one however.
            • Worth noting the shorter you go in the UV spectrum in terms of wavelength, the more dangerous it becomes.  Visible and longer wavelength parts of the spectrum are incapable of ionising atoms + molecules as their photon energy is insufficient. There are many molecular interactions that are possible with the 'longer stuff' but not  AB* = AB+ + e-  ie. the complete removal of an electron (singlet oxgen and ozone layer stuff). Not that far below 400nM the photon energy is high enough to effect ionisation and this becomes increasingly dangerous the lower you go; if you are unsure of your short wavelength sources don't over-expose!
            • Atmospheric absorbtion and enhanced scattering limits the range but for those interested in NLOS there maybe possibilities over moderate distances.

            regards de Russ ... g8bhh/g4pbp

          • d29602960
            Hi Gordon & Russ, Thanks to you both for the interesting and informative feedback on uv light sources. It was indeed the scattering potential of uv and blue
            Message 5 of 14 , Aug 13, 2012
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              Hi Gordon & Russ,

              Thanks to you both for the interesting and informative feedback on uv light sources.

              It was indeed the scattering potential of uv and blue light that caught my interest.

              Given the risks relating to uv it would seem blue light might be the safer option for optical scattering experiments?

              Regards.

              Des.

              --- In UKNanowaves@yahoogroups.com, Russ Stewart <g4pbp@...> wrote:
              >
              > On 12/08/2012 15:01, Gordon Fiander wrote:
              > >
              > > Hi Des,
              > >
              > > Barry is out today---regarding advantages of one part of the spectrum
              > > versus another ---visible red is probably the easiest frequency to
              > > work with---red propagates well through the atmosphere and photo diode
              > > based receivers are still reasonably efficient at 630nm. IR
              > > frequencies around 850nm look promising and photo diodes have peak
              > > response / efficiency at IR. However, you need to be very careful with
              > > higher power devices---eye damage. UV is perhaps one of the most
              > > challenging nanowave frequencies---UV is to red light what 24ghz is to
              > > HF. Photo diode response at UV is quite low and UV LEDs are qrp
              > > devices----one would need to take care with any higher power devices
              > > as at IR, At the moment we are just testing what is possible. Last
              > > night, nothing was visible at all of the UV source---we used a low
              > > power red LED for aiming/ sighting. Barry modulated the red source
              > > with JT4---something we tested a few months ago---and had a keyed tone
              > > on the UV. Once I pointed my RX at the red source I could hear both
              > > the JT4 tones and Barry's cw indent---the red light was then turned
              > > out, leaving the (invisible at my end) UV source.
              > > I suppose an advantage of UV is that the police get fewer reports of
              > > UFO's (Joking).
              > > Bernie's Finningley TCVR is a very good RX---on a par with Clint's
              > > design for baseband RX at all nanowave frequencies---it isn't just for
              > > nanowave novices,
              > >
              > > Best wishes
              > >
              > > ------------------------------------------------------------------------
              > > To: UKNanowaves@yahoogroups.com
              > > From: d29602960@...
              > > Date: Sun, 12 Aug 2012 12:32:27 +0000
              > > Subject: [UKNanowaves] Re: UV tests
              > >
              > > Hi Barry,
              > >
              > > Congratulations on you recent success with UV LED's.
              > >
              > > Do you think the UV part of the spectrum offers any advantages in
              > > through-the-air optical comms over red or green wavelengths?
              > >
              > > Regards,
              > >
              > > Des (M0AYF)
              > >
              > > --- In UKNanowaves@yahoogroups.com
              > > <mailto:UKNanowaves%40yahoogroups.com>, Barry Chambers
              > > <b.chambers@> wrote:
              > > >
              > > > Evening All
              > > >
              > > > Over the past week, Gordon G0EWN and I have been doing some tests using
              > > > UV radiation. This evening, we managed a 10km one-way contact from
              > > > G8AGN/P (Roper Hill, Sheffield) to G0EWN/P (Skew Hill, Sheffield).
              > > > Gordon gave me a report of 569 even though the sky was not fully
              > > dark by
              > > > 21.30. Visibility across our usual test path was poor and the UV
              > > > transmitter was not visible from the receive end.
              > > >
              > > > Equipment details are as follows:
              > > >
              > > > Tx
              > > > --
              > > >
              > > > 20 mw(dc input) UV LED (Maplin), measured output around 391nm
              > > (nominally
              > > > 400nm). The LED was CW keyed with a 976Hz tone using a PIC keyer.
              > > > Transmitter antenna was a A4 Fresnel lens.
              > > >
              > > > Rx
              > > > --
              > > > Standard Bernie kit baseband Rx with a A4 Fresnel lens antenna.
              > > >
              > > > No scintillation was noticed on the received signal which continued to
              > > > become stronger during the period of the test (21.00 - 21.30)
              > > >
              > > >
              > > > --
              > > >
              > > > 73
              > > > Barry, G8AGN
              > > >
              > >
              > >
              > >
              > Hi guys and of course congratulations on the latest UV tests. As with
              > most parts of the spectrum there are advantages and disadvantages.
              >
              > * Mie scattering becomes significantly better @ 400nM or there abouts
              > when compared to 630nM and IR. Thus for qso's around corners 400nM
              > is an advantage. <http://www.philiplaven.com/mieplot.htm>
              > * At ~ 400nM there is a weak eye response as well as a poorer
              > performance from our regular silicon photodetectors. There are very
              > sensitive instrument detectors available but they tend to be costly.
              > * There are 50W 400 nM LED arrays available on EBAY from time to time.
              > I think these are for aquarium illumination. They are safe in this
              > application as any short wavelength stuff will be filtered out by
              > water molecules. I would like to see the emission spectrum before
              > using one however.
              > * Worth noting the shorter you go in the UV spectrum in terms of
              > wavelength, the more dangerous it becomes. Visible and longer
              > wavelength parts of the spectrum are incapable of ionising atoms +
              > molecules as their photon energy is insufficient. There are many
              > molecular interactions that are possible with the 'longer stuff' but
              > not AB^* = AB^+ + e^- ie. the complete removal of an electron
              > (singlet oxgen and ozone layer stuff). Not that far below 400nM the
              > photon energy is high enough to effect ionisation and this becomes
              > increasingly dangerous the lower you go; if you are unsure of your
              > short wavelength sources don't over-expose!
              > * Atmospheric absorbtion and enhanced scattering limits the range but
              > for those interested in NLOS there maybe possibilities over moderate
              > distances.
              >
              > regards de Russ ... g8bhh/g4pbp
              >
            • Barry Chambers
              Des Sorry for the delay in replying but I was away at a family do yesterday. I think that red light is probably the best for most amateur nanowave work,
              Message 6 of 14 , Aug 13, 2012
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                Des

                Sorry for the delay in replying but I was away at a family "do" yesterday.

                I think that red light is probably the best for most amateur nanowave
                work, especially if you are only just starting. Red light can be seen
                which is good both from the safety angle and from ease of alignment
                during contacts, equipment adjustment etc.

                I did toy at one time with using green light rather than red. I have
                some green (and blue) high power LEDs but there is a limit to the number
                of hours in a day. I was intrigued by the UV demonstration which Stuart
                gave at Finingley and in a rash moment of boredom decided to "have a
                dabble". As ever, Gordon was only too willing to have his arm twisted!

                IR is a double-edged sword. It should propagate better but is invisible.
                This makes it more hazardous when high power sources are used (no
                automatic eye reflex to bright lights) and alignment can only be done
                using an auxillary visible light source (red light again).

                UV can be very dangerous if very short wavelengths are used. As Russ has
                pointed out, the shorter the UV wavelength the more hazardous it
                becomes. Luckily the Earth's atmosphere filters out most of the short
                wavelength UV! The Maplin LED source that Stuart and I are using is low
                powered (runs at 20ma max), emits nominally at 400nm (mine has been
                measured at 391nm - thanks to John, G8FDJ)and is therefore pretty safe
                unless perhaps you were to stick it close to your eye for some time (UV
                can cause cataracts). The LED emits a visible purple glow and so you are
                aware that it is switched on. It also causes fluorescence in white paper
                etc. If atmospheric conditions are good, a UV source of this power can
                be seen, certainly through binoculars, over a DX of at least 4km as
                Gordon can confirm from one of our tests last week. During our 10km
                test, however, the atmosphere was quite misty and the UV source could
                not be seen even though it was being received at 5-6-9.
                Russ mentioned that higher power UV LEDs are available. I feel these
                would have to be used with some caution. As Gordon has said "certainly
                not for the nanowave novice". Gordon has used Bernie's kit Rx for all
                our UV tests. It does, however, use a 2N5457 FET, rather than the '59
                supplied as part of the kit.


                73
                Barry, G8AGN
              • Barry Chambers
                Des Blue light might also be a problem if high powers are used. Do a Google search for blue light hazard 73 Barry, G8AGN
                Message 7 of 14 , Aug 13, 2012
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                  Des

                  Blue light might also be a problem if high powers are used.

                  Do a Google search for "blue light hazard"


                  73
                  Barry, G8AGN
                • g8cyw
                  Barry, Gordon, May I add my belated congrats on your 10km contact to those who have already done so, now I am back. Shades of last year here! It s hard isn t
                  Message 8 of 14 , Aug 13, 2012
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                    Barry, Gordon,

                    May I add my belated congrats on your 10km contact to those who have already done so, now I am back. Shades of last year here!

                    It's hard isn't it?! What fun!

                    I note you had to wait until 21.30 also, and that you are using the Fresnels at either end, the same LED, and baseband CW. These differences will help inform ongoing exploration on UV, I note that the activity has also generated some interesting comments here.

                    We too noted that there was nothing that could be seen at the range we were using, although on an earlier test, the violet glow was discernible at 1km in full daylight. Brian used my beacon as a guide since I was operating about 3m away from it, I transmitted LSB some 3kHz hf of the beacon and he could pick up both signals on his FT-817. Brian did not have a vis red beacon with him otherwise we might have had a two-way QSO, plus we started a bit early for the light level.

                    We will get straight back on this!

                    Regards,

                    Stuart



                    --- In UKNanowaves@yahoogroups.com, Barry Chambers <b.chambers@...> wrote:
                    >
                    > Evening All
                    >
                    > Over the past week, Gordon G0EWN and I have been doing some tests using
                    > UV radiation. This evening, we managed a 10km one-way contact from
                    > G8AGN/P (Roper Hill, Sheffield) to G0EWN/P (Skew Hill, Sheffield).
                    > Gordon gave me a report of 569 even though the sky was not fully dark by
                    > 21.30. Visibility across our usual test path was poor and the UV
                    > transmitter was not visible from the receive end.
                    >
                    > Equipment details are as follows:
                    >
                    > Tx
                    > --
                    >
                    > 20 mw(dc input) UV LED (Maplin), measured output around 391nm (nominally
                    > 400nm). The LED was CW keyed with a 976Hz tone using a PIC keyer.
                    > Transmitter antenna was a A4 Fresnel lens.
                    >
                    > Rx
                    > --
                    > Standard Bernie kit baseband Rx with a A4 Fresnel lens antenna.
                    >
                    > No scintillation was noticed on the received signal which continued to
                    > become stronger during the period of the test (21.00 - 21.30)
                    >
                    >
                    > --
                    >
                    > 73
                    > Barry, G8AGN
                    >
                  • Gordon Fiander
                    Hi Stuart, Barry and I conducted a series of tests over a few nights. The first test was around 100m followed shortly after by a 600m test, at Redmires west of
                    Message 9 of 14 , Aug 13, 2012
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                      Hi Stuart,

                      Barry and I conducted a series of tests over a few nights. The first test was around 100m followed shortly after by a 600m test, at Redmires west of Sheffield. This was just to confirm we had a signal. On the way home we tried the 10k path--I thought I detected Barry's tone but it was inconclusive--both of us were having aiming issues. A day or so latter we tried a 4k path---signals were established quite quickly---I could just make out the 'violet ' from Barry's TX---have a (poor) photo of this and a short bit of video where you can hear Barry's CW ident. All these initial tests were with 4 inch optics---no filtering--still to try using filters.A couple of nights latter we tried our 10k path, having both altered our systems to use Fresnel lens optics. Barry was a very solid copy--I gave him 569----similar to the results over the 4k path with 4 inch optics. Signal strength was still increasing as it started to get dark.  It is very likely signals would have been 599 had we waited for truly dark conditions----our photon range testing clearly demonstrates ANY additional light degrades signals, such is the nature and sensitivity of the RX. It is  worth noting that Bernie's Finningley RX is a very good performer-- on a par with Clint's RX at baseband.

                      Best wishes, 73s Gordon


                    • Barry Chambers
                      Hi Stuart Many thanks for your comments. We still only have one Tx and so you have a good chance of making a 2 way before us! Whether DX longer than 10km is
                      Message 10 of 14 , Aug 13, 2012
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                        Hi Stuart

                        Many thanks for your comments. We still only have one Tx and so you have
                        a good chance of making a 2 way before us! Whether DX longer than 10km
                        is possible with such low power sources, time will tell. I'm rather
                        diffident about using higher power devices because of local eye hazard.
                        More investigation is needed here. With UV there seems to be a double
                        whammy limiting DX. Firstly our silicon based detectors are running out
                        of sensitivity at 400nm and secondly lenses are starting to become opaque.


                        73
                        Barry, G8AGN
                      • g8cyw
                        Barry, I am catching up on this rapidly, thanks for your extra comments, and those from Gordon as well, it seems like you have had a similar number of outings
                        Message 11 of 14 , Aug 13, 2012
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                          Barry,

                          I am catching up on this rapidly, thanks for your extra comments, and those from Gordon as well, it seems like you have had a similar number of outings to us in getting UV "off the ground". I should not be so precious about the first two-way, since it has already happened in March for us over a short 250m path which I reported in at the time, we have always been intent on two-way QSOs from the onset since we are operating fully PTT using the transverter, we will probably go back to the 6km site first, before "pushing the envelope".

                          I find your comments and information most useful, from the datasheet I think we can say that we are operating using in the region of 10mW output power. Your comments about lenses, I had tried measuring the attenuation of the glass lenses but in reality, I do not think a few mm of glass is going to be a problem, I could not measure any attenuation at all when I did a rough check. I think the acrylic of the 3mm thick Fresnel lenses should be virtually transparent also, we are using UV that is only just outside the visible spectrum and therefore the lenses are at least nearly as good as in the visible spectrum, there being no observable colour cast. If the transmissivity were going to slope off at the short wavelength end I can't see it. I don't think it does to any pronounced extent.

                          Point taken about power level, much more powerful UV LEDS are available, frighteningly so! It is going to be interesting to see how we can eke out the 10mW over a few km, it certainly means we can employ our well-known favourite short paths easily.

                          I actually used the 6km path to test the first of my red LED transceivers where the LED was actually a 5mm low power through hole type before I discovered I could do the same trick with the Golden Dragons on receive. The chap at the other end still gave me 5 and 9 plus!

                          From previous work on glass 4" lenses compared to the page magnifiers, it seems there is an 8dB advantage in going to the Fresnel I have discovered using red light on both TX and RX separately, of course using Fresnels at both ends would then yield 16dB more gain which translates to an increase in range of over 6 times minus the extinction coefficient of course, which might be greater at UV.

                          I think we will stick to the 4" systems and 10mW LEDs at present and see where we get to, it is nice to have a new challenge!


                          Regards to all,

                          Stuart


                          --- In UKNanowaves@yahoogroups.com, Barry Chambers <b.chambers@...> wrote:
                          >
                          > Hi Stuart
                          >
                          > Many thanks for your comments. We still only have one Tx and so you have
                          > a good chance of making a 2 way before us! Whether DX longer than 10km
                          > is possible with such low power sources, time will tell. I'm rather
                          > diffident about using higher power devices because of local eye hazard.
                          > More investigation is needed here. With UV there seems to be a double
                          > whammy limiting DX. Firstly our silicon based detectors are running out
                          > of sensitivity at 400nm and secondly lenses are starting to become opaque.
                          >
                          >
                          > 73
                          > Barry, G8AGN
                          >
                        • d29602960
                          Good evening Barry, Barry wrote: Sorry for the delay in replying but I was away at a family do yesterday. ********** No problem, thanks for taking the time
                          Message 12 of 14 , Aug 13, 2012
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                            Good evening Barry,

                            Barry wrote:
                            Sorry for the delay in replying but I was away at a family "do" yesterday.
                            **********

                            No problem, thanks for taking the time to respond and in particular for drawing my attention to the "blue light hazard" which I found particularly interesting.

                            I supose it should be no surprise that the hazards become greater as the wavelength gets shorter but it did make me wonder about the lights they use to treat the symptoms of "SAD" (Seasonal affective disorder)which have quite a bit of blue light in them. According to Wikipedia the treatment includes light sources which contain blue light at a wavelength of 480 nm at 2,500 lux.

                            http://en.wikipedia.org/wiki/Seasonal_affective_disorder#Treatment

                            If I pursue any scattering experiments with blue light I will be sure to keep the power low and make sure no-one will be tempted to stair at the light for long periods.

                            73,

                            Des (M0AYF)

                            --- In UKNanowaves@yahoogroups.com, Barry Chambers <b.chambers@...> wrote:
                            >
                            > Des
                            >
                            > Sorry for the delay in replying but I was away at a family "do" yesterday.
                            >
                            > I think that red light is probably the best for most amateur nanowave
                            > work, especially if you are only just starting. Red light can be seen
                            > which is good both from the safety angle and from ease of alignment
                            > during contacts, equipment adjustment etc.
                            >
                            > I did toy at one time with using green light rather than red. I have
                            > some green (and blue) high power LEDs but there is a limit to the number
                            > of hours in a day. I was intrigued by the UV demonstration which Stuart
                            > gave at Finingley and in a rash moment of boredom decided to "have a
                            > dabble". As ever, Gordon was only too willing to have his arm twisted!
                            >
                            > IR is a double-edged sword. It should propagate better but is invisible.
                            > This makes it more hazardous when high power sources are used (no
                            > automatic eye reflex to bright lights) and alignment can only be done
                            > using an auxillary visible light source (red light again).
                            >
                            > UV can be very dangerous if very short wavelengths are used. As Russ has
                            > pointed out, the shorter the UV wavelength the more hazardous it
                            > becomes. Luckily the Earth's atmosphere filters out most of the short
                            > wavelength UV! The Maplin LED source that Stuart and I are using is low
                            > powered (runs at 20ma max), emits nominally at 400nm (mine has been
                            > measured at 391nm - thanks to John, G8FDJ)and is therefore pretty safe
                            > unless perhaps you were to stick it close to your eye for some time (UV
                            > can cause cataracts). The LED emits a visible purple glow and so you are
                            > aware that it is switched on. It also causes fluorescence in white paper
                            > etc. If atmospheric conditions are good, a UV source of this power can
                            > be seen, certainly through binoculars, over a DX of at least 4km as
                            > Gordon can confirm from one of our tests last week. During our 10km
                            > test, however, the atmosphere was quite misty and the UV source could
                            > not be seen even though it was being received at 5-6-9.
                            > Russ mentioned that higher power UV LEDs are available. I feel these
                            > would have to be used with some caution. As Gordon has said "certainly
                            > not for the nanowave novice". Gordon has used Bernie's kit Rx for all
                            > our UV tests. It does, however, use a 2N5457 FET, rather than the '59
                            > supplied as part of the kit.
                            >
                            >
                            > 73
                            > Barry, G8AGN
                            >
                          • Russ Stewart
                            ... Me again. As Stuart says, transparency should not be a problem. Down to 320-330nM decent glass and acrilics are very transparent although from memory,
                            Message 13 of 14 , Aug 13, 2012
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                              On 13/08/2012 17:46, g8cyw wrote:
                               

                              Barry,

                              I am catching up on this rapidly, thanks for your extra comments, and those from Gordon as well, it seems like you have had a similar number of outings to us in getting UV "off the ground". I should not be so precious about the first two-way, since it has already happened in March for us over a short 250m path which I reported in at the time, we have always been intent on two-way QSOs from the onset since we are operating fully PTT using the transverter, we will probably go back to the 6km site first, before "pushing the envelope".

                              I find your comments and information most useful, from the datasheet I think we can say that we are operating using in the region of 10mW output power. Your comments about lenses, I had tried measuring the attenuation of the glass lenses but in reality, I do not think a few mm of glass is going to be a problem, I could not measure any attenuation at all when I did a rough check. I think the acrylic of the 3mm thick Fresnel lenses should be virtually transparent also, we are using UV that is only just outside the visible spectrum and therefore the lenses are at least nearly as good as in the visible spectrum, there being no observable colour cast. If the transmissivity were going to slope off at the short wavelength end I can't see it. I don't think it does to any pronounced extent.

                              Point taken about power level, much more powerful UV LEDS are available, frighteningly so! It is going to be interesting to see how we can eke out the 10mW over a few km, it certainly means we can employ our well-known favourite short paths easily.

                              I actually used the 6km path to test the first of my red LED transceivers where the LED was actually a 5mm low power through hole type before I discovered I could do the same trick with the Golden Dragons on receive. The chap at the other end still gave me 5 and 9 plus!

                              >From previous work on glass 4" lenses compared to the page magnifiers, it seems there is an 8dB advantage in going to the Fresnel I have discovered using red light on both TX and RX separately, of course using Fresnels at both ends would then yield 16dB more gain which translates to an increase in range of over 6 times minus the extinction coefficient of course, which might be greater at UV.

                              I think we will stick to the 4" systems and 10mW LEDs at present and see where we get to, it is nice to have a new challenge!

                              Regards to all,

                              Stuart

                              --- In UKNanowaves@yahoogroups.com, Barry Chambers <b.chambers@...> wrote:
                              >
                              > Hi Stuart
                              >
                              > Many thanks for your comments. We still only have one Tx and so you have
                              > a good chance of making a 2 way before us! Whether DX longer than 10km
                              > is possible with such low power sources, time will tell. I'm rather
                              > diffident about using higher power devices because of local eye hazard.
                              > More investigation is needed here. With UV there seems to be a double
                              > whammy limiting DX. Firstly our silicon based detectors are running out
                              > of sensitivity at 400nm and secondly lenses are starting to become opaque.
                              >
                              >
                              > 73
                              > Barry, G8AGN
                              >

                              Me again. As Stuart says, transparency should not be a problem.

                              Down to 320-330nM decent glass and acrilics are very transparent although from memory, cheap soda glass starts to absorb down there. I doubt if the sources we are using will go that short in wavelength, at least I hope not.

                              Although the really nasty UV really starts below 200nM, (ionisation), as I said in my last offering there are many chemical reactions that can be photo-induced with softer UV, some desirable and some not. Most of us like a bit of UVB to get a suntan and synthesise Vitamin D but the medical types say forget the tan and take a supplement; well they would would't they :-)

                              I hope I did not frighten anyone into not playing UV comms. Mostly using the stuff we play with any danger is minimal and always remember what matters is flux density x exposure time so we have a degree of control.

                              For fun and if you are interested, take a look at these uTube videos. Firstly a 405nM laser you can go out and buy for < £100and secondly an industrial Eximer UV laser at I think 150nm and what it does to the atmosphere. I hope you can't easily buy these :-)


                              http://www.youtube.com/watch?v=qB0F1yR0LIY&feature=related

                              http://www.youtube.com/watch?v=GXxG6e5GoKI

                              regards de Russ g8bhh/g4pbp
                            • g8cyw
                              Thanks for confirmation on transparency Russ, and I like those videos! I think I will stick with the 10mW LEDs thanks!!! Stuart
                              Message 14 of 14 , Aug 13, 2012
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                                Thanks for confirmation on transparency Russ, and I like those videos!
                                I think I will stick with the 10mW LEDs thanks!!!

                                Stuart


                                > Me again. As Stuart says, transparency should not be a problem.
                                >
                                > Down to 320-330nM decent glass and acrilics are very transparent
                                > although from memory, cheap soda glass starts to absorb down there. I
                                > doubt if the sources we are using will go that short in wavelength, at
                                > least I hope not.
                                >
                                > Although the really nasty UV really starts below 200nM, (ionisation), as
                                > I said in my last offering there are many chemical reactions that can be
                                > photo-induced with softer UV, some desirable and some not. Most of us
                                > like a bit of UVB to get a suntan and synthesise Vitamin D but the
                                > medical types say forget the tan and take a supplement; well they would
                                > would't they :-)
                                >
                                > I hope I did not frighten anyone into not playing UV comms. Mostly using
                                > the stuff we play with any danger is minimal and always remember what
                                > matters is /flux density x exposure time/ so we have a degree of control.
                                >
                                > For fun and if you are interested, take a look at these uTube videos.
                                > Firstly a 405nM laser you can go out and buy for < £100and secondly an
                                > industrial Eximer UV laser at I think 150nm and what it does to the
                                > atmosphere. I hope you can't easily buy these :-)
                                >
                                >
                                > http://www.youtube.com/watch?v=qB0F1yR0LIY&feature=related
                                >
                                > http://www.youtube.com/watch?v=GXxG6e5GoKI
                                >
                                > regards de Russ g8bhh/g4pbp
                                >
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