[Lowfer] SWR meters for LowFERs

[Bill Ashlock]

Lyle,

>your measurements indicating low harmonic content are probably
>correct,......  >But I like to be able to go to the end of my driveway >and 
>find no trace of LEK harmonics on the AM broadcast band, so I'll >keep the 
>filter in the circuit.

I just re-tested for AM band harmonics on my car radio at the end of the 
driveway, but considerably closer to the antenna than the end of your 
driveway. No harmonic of 185.300 has the frequency any station within 100mi 
but at the strongest harmonic I could barely make out a 'WA' when running at 
normal CW speeds. I'm sure the untrained listener could not have heard 
anything except background signals 100s of miles away. (This radio is pretty 
hot)

>The loop matching transformer doesn't inherently attenuate high 
> >frequencies. Type 43 and 77 material can be used in broadband 
> >transformers and baluns through the HF range.

Yes, I just discovered this, and I thank your for pointing out the error of 
my way. My wrong assumption was due to the specifications indicating the two 
core types are good for tuned filters up to ~1Mhz. I just ran a bench test 
on the same core that I use for my stepdown transformer and it makes a nice 
broadband transformer up to 20 MHz

>However, the transformer steps down the voltage from
>the transmitter, and the loop exhibits a fairly high reactance until it
>reaches the first resonance at 5 MHz, so you are correct that not much >HF 
>current flows in the loop.

Yes, the stepdown in voltage amounts to about 23db for my main loop setup 
and this could well be the main reason for the lack of strong harmonics.

>By the time you get to 5 MHz, the harmonic content from the >transmitter is 
>very low anyway. I expect that the same
>thing is true for vertical antennas, although the analysis is more
>complicated because of possible stray resonances in the loading coil.

Agree.

>It would be interesting to try a loop at my location, but there are >three 
>reasons why I haven't done so:

>1. No convenient 50-foot high trees that could support a heavy loop.

Com-mon.... no big pipes allowed! The rule of 185k loopland is that 
newcommers must start with a #12 wire to get the 'feel' of these things :) I 
saw a picture showing a big tree and a tower that would make ideal supports.
>
>I've already got a LowFER antenna that ain't busted!

Have you checked your signal lately? We loopers take no prisoners! :)
(Mike, did you carry out that assignment?)

Seriously, a bunch of us are looking for a sight that could operate both a 
loop and a vertical. An antenna factor, something like 6db, can  be added at 
the receiving site to compensate for a #12 wire instead of the 1" pipe. 
Please give it a thought.

Wild Bill


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