How to test UHF antenna
David
My GWE UHF 3420 unit mounted in my 4WD lacks sensitivity - that is, it
is clearly outperformed on reception by my GWE 6200 handheld - eg on the
handheld I could clearly hear a conversations on channel 1 whereas on
the car set the signal was either so noisy that the speech was
intelligible or else the squelch, on the most sensitive setting,
"blocked" the signal and hence all was quiet.
The vehicle set is attached to a GWE 4.5db no-groundplane-required
antenna with spring mount base on the bull bar whereas the hand held
(GWE 6200) just has its 6" antenna)
Since the receiver specs are identical on both units I would expect the
car set with its 1 metre antenna to at least equal the handhelds
performance.
How can i check the antenna? Only test gear I have is a multimeter and
a CRO - no sig gen etc.
What sort of measurement should I get in terms of resistance across the
antenna - eg checking centre core to braid on antenna lead at the set
end. Should it read o/c or is there a coupling coil or such in the
antenna itself, and thus a low ohm reading?
I would appreciate ideas and suggestions
David
PS I am not able to check xmitting performance
Suzy
"David" <post...@REMOVE-TO-REPLYconfidential-counselling.com> wrote in
message news:postings-E44514...@news.ceinternet.com.au...
Have come across many installations where the antenna is seriously detuned
by adjacent parts of the bullbar, like a few cms above the base.
sparkyau
Hi David,
Remove the aerial from the base if you check across the bottom of the
aerial you will have circuit that is the way that type of aerial is
made.
Now check your coax you should have circuit from end to end with the
centre conductor and also the braid.
If you check across the end of the coax centre to braid there should
be no circuit.
Where are you from please.
Cheers
Gavin
Hobart
David
slackj <slackj...@optusnet.com.au> wrote:
> Have you tried the 6200 with a TNC - SO239 adaptor to establish that
> the antenna or co-ax is faulty rather than the mounted transceiver
> being deaf?
>
>
Tanks for your reply
Yes, but not lately. Originally I bought the ext antenna for the 6200
to increase its range, but it didn't make much difference so didn't use
it after the 1st week or so.
Then because the 6200 switched its backlight off after a few seconds
which meant at night I couldn't see what channel was in use, I bought
the car unit which has its backlight on all the time.
Measuring across the receiver end plug it showed a very low resistance -
eg a short. So have now replaced the fitting and that measurement is
now o/c with the antenna whip on.
Performance now seems a but better but as yet I haven't been able to doa
comparison with the 6200
Cheers
David
David
<b1b5cbb5-7f00-43b9...@s19g2000prg.googlegroups.com>,
sparkyau <vk7...@gmail.com> wrote:
>
> Hi David,
> Remove the aerial from the base if you check across the bottom of the
> aerial you will have circuit that is the way that type of aerial is
> made.
> Now check your coax you should have circuit from end to end with the
> centre conductor and also the braid.
> If you check across the end of the coax centre to braid there should
> be no circuit.
> Where are you from please.
> Cheers
> Gavin
> Hobart
OK tried that and it measured short circuit - had a new end fitting
attached and now reads o/c
I haven't had a chance to retest it against the 6200 as yet but will do
so in a day or so
thanks for your reply
cheers\\David
Kev
if you want better RX performance move the antenna from the bullbar as
it has no ground plane and place it up higher on the front guard or roof
or you could purchase an elevated feed antenna, these are ground
independent antennas(the elevated feed acts as a ground)
Kev