Re: [softrock40] Softrock v 7.0 as transverter IF
- Thanks for the note, John!
Let me know if I can be of assistance.
The ESS will be easier to setup, and should be OK unless you have
potential for overload. In that case the SR7 may be better.
On Thu, 25 May 2006 09:16:15 -0400, John D'Ausilio <jdausilio@...>
> tnx for the info Roger .. I've got an SR7 as well as an ESS Time--
> Machine set up for 28 Mhz IF .. hopefully will have time to integrate
> into RX chain before June, Sept for sure. Probably going to have to
> use USB SB Live for sound, at least until I get a car PC into the
> rover with a PCI slot :)
> de w1rt/r john
> On 5/24/06, w3sz <w3sz@...> wrote:
>> Hi, All,
>> I built a Softrock v 7.0 today and have just a brief report of my first
>> experience with using it as a transverter IF.
>> I also built a KK7B-designed R2Pro LNA which I had gotten from Kanga
>> as I thought I would need it in front of the Softrock with my current
>> setup, and I was correct about this.
>> The building of the Softrock went smoothly as usual, due to Tony Parks'
>> excellent instructions.
>> The only recommendation I have for those constructing the unit would be
>> use a bit of Testor's model paint or something similar to paint the two
>> ends of one of the transformer secondary wires red, the ends of the
>> wire blue, the ends of the third wire yellow, so that the 4 wires can be
>> easily sorted before they are put through the holes in the circuit
>> I did OK without this, but it would be easy to mix things up. One could
>> go even further and give each end of each wire a different color, but
>> seems a bit excessive to me ;)
>> I used one of my PTS synthesizers as the LO, rather than using the xtal.
>> The v7 needed much less LO drive than the v6's I built. The output
>> on the PTS160 was barely above zero, and I measured the PTS output
>> to get good function of the v7 as -7.2 dBm with both an HP435B and a
>> Boonton 4200. That would be about 2/10 of a milliwatt LO power
>> I fed the LO into the v7 where the xtal would ordinarily be placed.
>> I tested things without having either the Softrock or the LNA in a box,
>> and with no attempt to keep leads short or follow good grounding
>> practices, as this was just a preliminary test to see if my first
>> at building a v7 was successful.
>> I found that using the R2PRO LNA [which is specified to give +13 dB gain
>> and have a noise figure of about 2 dB and good dynamic range] was
>> necessary to get adequate signal gain when using the v7 with a DownEast
>> Microwave 50 MHz transverter which was set to give MORE than receive
>> optimal signal levels to my FT1000MP. Adding even more gain in the form
>> a Q-Bits QBH9-154 placed in front of the R2PRO LNA increased signal
>> further by about 5 dB, but did not improve readability and so the net
>> effect of adding the Q-Bits amplifier was just to reduce system dynamic
>> range. I should have tried placing it after the LNA, since the LNA
>> provides some bandpass filtering, but did not do so [see below for why].
>> Using Linrad to measure the noise floor, it was about 20 dB [relative
>> units] without the R2PRO LNA and about 35 dB with the R2PRO LNA,
>> consistent with the design target of 13 dB gain. Signals were brought
>> of the noise by the R2PRO LNA and I had no problems with overload when
>> using it.
>> During the middle of my testing 6 meters suddenly opened to the mid-west
>> [I am in Eastern PA, in FN20] and I suddenly began hearing K0HGP and
>> mid-western stations blasting in, so I sort of got sidetracked in my
>> testing until the opening disappeared ;)
>> As usual, the zero-frequency hump was noticeable but produced no
>> So in summary, the Softrock v7 did well for me today in its first trial
>> an IF radio. The PTS worked well as LO and less drive was required from
>> it than with the v6 Softrocks. I needed additional gain in the form of
>> R2PRO LNA for optimal receive performance. How much gain you will need
>> front of the Softrock depends upon the details of your receive chain.
>> My receive chain from antenna to Softrock was:
>> M2 6M5X to SSB Electronics SP6 mast-mounted preamp to 120 feet of LMR600
>> to 140 feet 7/8 inch hardline to DEM transverter to Mini-circuits 2way
>> splitter to R2PRO LNA to Softrock. The other splitter output went to
>> FT1000MP. As noted above, I tested the effect of further amplification
>> with a Q-Bits amplifier [and also with the preamp in my Mirage 6 meter
>> amp]. Neither improved readability and so neither was kept inline.
>> I hope the above is of some help and some interest.
>> Thanks, Tony, for the great project you have given us!
>> Roger Rehr
>> Roger Rehr
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