Jim,
I'm interested in the VNWA's 160m performance in the presence of local
broadcast stations. When designing a Marconi "T" for N4NN, we deliberately
resonated the antenna to 1400 kHz which called for a VNA sweep below
resonance. Two local 5KW BC stations are at 1400 kHz and 1460 kHz, with the
latter being only about five miles to the south of N4NN's QTH.
We used an N2PK VNA which has potent output power and MyVNA software that
does a nice job of discriminating against interference. As you can imagine,
the field strength of the two BC stations at the antenna feed is huge,
especially when the antenna is resonant to the nearby stations. Yet, the
plots only show a slight "blip" in the R and X sweeps.
Since the VNWA unit's output power is about 10 dB less than the N2PK units -
and I believe the entry-level model of the W5BIG units, it would be
interesting to see how well these hold up in the presence of really strong
BC field strength. I have saved the N4NN plot if you are ever in a position
to look at 160m performance with nearby BC stations -- even if the antenna
is not resonant below 160m.
If $$$ was no object, I'd go for the R&S FSH424 with VNA option. But,
that's about USD $16K, loaded. For now, the N2PK VNA works extremely well
for HF purposes, and a used Agilent N1996A-TG S/A was just added to the work
bench.
For folks looking for a spectrum analyzer and who can live with res.
bandwidth to 100 Hz, take a look at the new Rigol DS815. Without TG, price
is about USD $1300 new. With TG, it's USD $1500. Looks like a great value
although I know nothing of Rigol's after-sale support.
Paul, W9AC
----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: <towertalk@contesting.com>
Sent: Tuesday, July 10, 2012 11:40 AM
Subject: Re: [TowerTalk] an antenna analyzer to drool over
> On 7/10/2012 3:58 AM, Dino Darling wrote:
>> You can get much of the same data for a whole lot cheaper here...
>> http://www.arraysolutions.com/Products/AIM4170.htm
>>
>
> The AIM units are expensive compared to this one, designed by DG8SAQ, a
> prof at a German university, and built and sold by hams in the UK. I
> paid $766 for mine, including calibration standards and a small case,
> and it arrived in about ten days. Very nice unit, free software by
> DG8SAQ that has excellent features and is in ongoing development. I've
> had it for about six weeks, and am quite pleased with it. One major
> advantage is that it is USB-powered, so I can take it out to where my
> antennas are without having to drag AC power. There's also a rather
> active Yahoo Group with some pretty sharp guys contributing.
>
> 73, Jim K9YC
> _______________________________________________
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