[Elecraft] OT:. G5RV's

[Wes Stewart]

The tuner loss also depends on how it is adjusted.  For example the very popular 
high-pass Tee with three adjustable elements has an infinite number of possible 
combinations that will effect a match on the same load Z.  One of them is the 
lowest loss solution, all of the others aren't.

As I said earlier, in a letter to Dean Straw dated February 2, 1994 I offered an 
example where the SPC tuner, then current in the handbooks, could be used to 
match an impedance of 4.34 +j46 to 50 ohm. (I forget where this came from but it 
was a real possibility)  I assumed Qc = 1000 and Ql = 300 (generous). I used 
Touchstone to calculate the minimum loss and maximum loss solutions The best 
case was 1.6 dB and the worst case was 7.8 dB.

With lower Q components, Qc = 500, Ql =200, the losses were 2.4 to 9.5 dB!

Wes  N7WS


  On 8/4/2016 2:00 PM, Alan Bloom wrote:
> > It's a pity that too many newcomers, as well as many oldsters, are
> > enamored by this piece of wire.
>
> The G4RV is definitely a compromise antenna.  However its advantage is that is 
> has low-enough SWR to be easily matched by most tuners on a number of bands.
>
> > ... the horrific losses that could be incurred even
> > with high quality tuners,
>
> It's true that tuner losses are the manufacturers' dirty little secret. Loss 
> is rarely specified, partly because it can be pretty bad, and partly because 
> it is hard to measure, but also because it is not constant - it depends on the 
> particular impedance being matched.
>
> One exception is the old Drake tuners.  Their Pi-L topology makes the loss 
> almost independent of the load impedance.  If you can get it to match, you 
> know that almost all the power is going into the feed line. For example, the 
> MN-2700 that I designed when I was at Drake was specified at 0.5 dB maximum 
> insertion loss and I did a lot of testing and tweaking to achieve that on all 
> bands.
>
> Alan N1AL