Nagoya NA-701 measurements
Mr. Benn
Measured on an Agilent network analyser, the return losses are
145MHz: 1.6dB (rubbish)
435MHz 7dB (ok)
The VHF resonance is centred lower than 145MHz, around 137MHz. Can I tune
this antenna up in frequency by cutting a few mm off the end? It looks like
it's a base-loaded sleeve dipole.
Ian Jackson
<inv...@invalid.invalid> writes
What sort of ground/groundplane did you use for the tests?
--
Ian
Mr. Benn
news:3dAIqQWw...@g3ohx.demon.co.uk...
No groundplane apart from my hand holding the shield of the SMA connector at
the base of the antenna. I'm assuming that the antenna is an electrically
short sleeve dipole.. Or is it?
Just clipped off a few mm of the end of the antenna. Surprisingly didn't
affect the frequencies of the two resonances all that much. Got the return
loss at 145MHz up to 2dB now! At peak of the VHF resonance (138MHz), the
return loss is 10dB
Andy Foad
Your results don't compare to mine.
I get a good match, so does everyone else, and so does everyone
else get excellent performance.
It must be you ;-)
Mr. Benn
news:cf8fbb94-69dc-4af7...@y19g2000yqk.googlegroups.com...
I have built several sleeve dipoles and none of them require a groundplane.
I get better than 10dB return loss on the ones I build myself. I was hoping
to see better than 2dB from the Nagoya offering. That's a VSWR of 9!
The network analyser I use is calibrated BTW.
Jeff
>
> I have built several sleeve dipoles and none of them require a
> groundplane. I get better than 10dB return loss on the ones I build
> myself. I was hoping to see better than 2dB from the Nagoya offering.
> That's a VSWR of 9!
>
> The network analyser I use is calibrated BTW.
Surely for it to be a sleeve dipole it would have to be of the order of
1/2 wavelength long (1/4 wave element plus 1/4 wave sleve). Since the
antenna in question is only 21cm long it seems somewhat short for even
1/4 wave on 2m. (unless what looks like a straight whip is helical in
some way).
Jeff
Mr. Benn
news:is5ju6$bjg$1...@speranza.aioe.org...
Yes, you're right, it's a long way from being a full size dipole., It has to
be electrically loaded in some way to make the length physically shorter. I
don't think it's a monopole as it isn't that sensitive to environment when I
look at it on a network analyser.
Andy Foad
> 145MHz: 1.6dB (rubbish)
I have _three_ of the Nagoya 701 antennas and I've
just checked all of them.
-13db return loss.
Perfect.
Can't understand why your having problems with yours.
How does it's on air performance appear ?
Richard G3CWI
> Measured on an Agilent network analyser, the return losses are
>
> 145MHz: 1.6dB (rubbish)
> 435MHz 7dB (ok)
A return loss of 7dB is pretty rubbish too.
mm0fmf
>
> Can't understand why your having problems with yours.
Is it a Nagoya or is it a "Nagoya"?
i.e. a real Nagoya or some cheap copy that looks the same?
Andy Foad
I thought Mr Benn obtained his from 409shop, same as me,
so should have no problems.
Like I said, I have of the 701's and I'm thinking of buying another,
that's how good I rate them.
I have a few other Nagoya's. They seem ok, no disasters, average.
But the 701 sticks out as being one that works well on both bands
and has maximum oomph for size.
The only antenna that beats it my Diamond SRH940 tribander,
and that's £35 worth as opposed to £7.
Mr. Benn
It receives signals but I haven't tried transmitting but then a
poorly-matched random length of wire will receive signals.
I appreciate that your antennas work and are well-matched but I think I've
been unlucky with mine. The measurements I made are valid and were
performed in a commercial RF development lab. The instrument I used is in
daily use by me and other engineers who confirmed the measurements I made.
Mr. Benn
news:ab43de1a-9dd8-4f89...@n11g2000yqf.googlegroups.com...
It's great compared to 1.6dB!
Jimbo....
>
> Is it a Nagoya or is it a "Nagoya"?
>
> i.e. a real Nagoya or some cheap copy that looks the same?
>
>
>
bit like finger guns then .......
Andy Foad
> I appreciate that your antennas work and are well-matched but I think I've
> been unlucky with mine. The measurements I made are valid and were
> performed in a commercial RF development lab. The instrument I used is in
> daily use by me and other engineers who confirmed the measurements I made.
Even so, I always question everyones work ;-)
During my work at UoK I had a PhD student
wishing to do some measurments on a DAB .
antenna and needed a groundplane
to simulate being on a vehicle.
We had a larger metal table with a hold drilled
especially for mounting such antennas.
PhD studend keep reporting that he cannot acheive a
decent match so I went and had a look.
Turn out he had antenna connected to coax, and then
20ft of wire from coax which was bonded to the metal table
across the workshop.
At this point I reached for some headache tablets ;-)