10659Re: [loopantennas] A bit OT: new delay line kit
- Jul 1, 2014On 7/1/2014 8:44 PM, 'pu3hag.l@...' pu3hag.l@...
> Hi,Well, research this:
> Chavdar Levkov, LZ1AQ - who runs active-antenna.eu
> <http://active-antenna.eu> - has included a
> 2nd kit to his site: delay lines for phases antenna array.
> I have one of his loop amplifiers still to build. I admit I have zero
> knowledge on delay lines and need to research a bit on this topic.
> -- pu3hag huelbe
I published this in 2008 and I see that LZ1AQ's delay
lines are virtually identical to the ones I described.
Maybe he reinvented this stuff. I have an unpublished
PC board design that uses jumpers exactly like the LZ1AQ
board. However, I learned the hard way not to try to
use a binary series of delays. Unless the delays are
exact, there will be gaps in coverage and the delay
you happen to need might be unrealizable. Instead, what I
do is to use a so-called "Radix 1.5" series with ratios
of: 1, 1.5, 2.25, 3.375, etc. instead of 1, 2, 4, 8 etc.
This has a substantial overlap and allows for fairly
sloppy tolerances. I got this idea from the ADC designers
at Agilent who used Radix 1.5 to eliminate missing codes.
They said everyone in the ADC community knows about this.
Except, the variable delay line is analogous to a DAC
instead of an ADC. Some principle though.
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