UHF and SWR
Submitted: Saturday, May 19, 2007 at 20:14
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phillip owen
Hi all,
Just bought a new GME 3220
UHF radio, CP474S (fibreglass with spring base) aerial (4.5dB) and approx. 5m of coaxial cable to connect the two.
My question is, can I go ahead and install the unit (on a Suzuki XL7) and begin using it, or do I need to SWR the unit/aerial set-up? The aerial will be on a 'Z' bracket on the side of the bonnet and then mounted on a bull bar in a couple of months. Will I need to SWR the set-up again when moved?
Cheers
Reply By: Dustin - Saturday, May 19, 2007 at 20:26
Saturday, May 19, 2007 at 20:26
Hi Philip,
As far as I have seen all UHF antennas come pre tuned, you really only needed an SWR meter for the am 27 Mhz radios.
If its a ground plane antenna you can move it to any location you like,
But I could be wrong :-)
AnswerID:
241069
Follow Up By: Member - Doug T (W.A) - Saturday, May 19, 2007 at 21:28
Saturday, May 19, 2007 at 21:28
Dustin
No your not wrong, and most 27mhz antennas are also pre-tuned
FollowupID:
501981
Follow Up By: Dustin - Saturday, May 19, 2007 at 21:40
Saturday, May 19, 2007 at 21:40
Doug, its been 25 years since I played with a 27 Mhz antenna and I needed one back then, obviously times have changed...Cheers.,
FollowupID:
501985
Follow Up By: Member - Doug T (W.A) - Saturday, May 19, 2007 at 22:24
Saturday, May 19, 2007 at 22:24
I still use one but even then it's not used all that much it's hooked up to one of these little beauts, one very nice radio
Features: PLL Synthesised mobile all mode tranceiver with large illuminated LCD Digital Bargraph Display, 5 digit LCD frequency readout Frequency: 25.160 - 29.700MHz (Export Version) Frequency Tolerance: 0.0005% Frequency Accuracy: 110ppm or better Output Power: 30watt AM/SSB/CW PEP & 25watt max. FM Spurious Emission: -60dB or better Carrier Suppression: -40dB or better Meter Functions: Signal S/RF, RX Receive Signal Strength, Modulation, SWR Calibration, SWR Others: Mic - 600 Ohms, Dynamic PTT Dimensions: Size 2 3/8" x 7 7/8" x 9 1/4" Weight 1.8kg
Manufacturer: DeltaForce
$549.00 incl. GST
FollowupID:
501996
Follow Up By: DarrynJ - Sunday, May 20, 2007 at 09:10
Sunday, May 20, 2007 at 09:10
Pirate special eh Doug? Dustin any HF antenna (RFDS VKS 737 or 27 MHZ) needs to be checked as they nearly always need a good earth for proper performance.
Regd's Darryn
FollowupID:
502023
Follow Up By: Member - Doug T (W.A) - Sunday, May 20, 2007 at 10:15
Sunday, May 20, 2007 at 10:15
Darryn
Aye yes there me Laddy, gets me fingers burnt every times I use it .
I don't worry much about the other frequencies much , talk a bit of skip in and around the 27mhz CB band , sometimes go up around 44 -50 , very rare these days though,
Doug
FollowupID:
502037
Follow Up By: DarrynJ - Sunday, May 20, 2007 at 17:01
Sunday, May 20, 2007 at 17:01
Cap'n Doug, I haven't turned the 27 MHZ set on for 12 + months, last time I turned it on there was nothing anywhere on the std 40 ch. I see just about all comms gear retailers have stopped selling 27 MHZ gear altogether. I wonder if the Fed Gov't will give the band space back to the Amateurs like they were supposed to in 1982 when the 27 MHZ was originally ment to close to CB.
Cheers Darryn
FollowupID:
502100
Follow Up By: Member - Doug T (W.A) - Sunday, May 20, 2007 at 18:01
Sunday, May 20, 2007 at 18:01
The Amateurs don't need 27mhz , besides too much noise can come from USA sometimes ,
Doug
FollowupID:
502110
Follow Up By: Mike Harding - Sunday, May 20, 2007 at 18:09
Sunday, May 20, 2007 at 18:09
And we have 24, 28 and 29 :) Not to mention 21, 18, 14, 10, 7, 3.5, 1.8, 146, 440, and heaps of other stuff above that if you're into SHF things.
Mike Harding
FollowupID:
502112
Follow Up By: Member - Doug T (W.A) - Sunday, May 20, 2007 at 18:17
Sunday, May 20, 2007 at 18:17
Mike
Yep I know what got and what you can use, I'm happy just to use what I have and VKS-737,
FollowupID:
502116
Reply By: Member - Steven H (ACT) - Saturday, May 19, 2007 at 20:28
Saturday, May 19, 2007 at 20:28
No need to SWR in the UHF antennas unless you area purist they are ready to go as supplied.
AnswerID:
241070
Reply By: Grungle - Sunday, May 20, 2007 at 09:24
Sunday, May 20, 2007 at 09:24
Hi Phillip,
If the ariel is one where you have to put the connector on yourself then
check the connector with an ohm meter to make sure it is not shorted (non dc grounded ariel) between the centre pin and outer connector. We see around 50% of all customer fitted connectors short or open in some way.
Also we have received 2 x 477MHz pre-tuned ariels from a reputable company in the past month that were out of tune and showing a VSWR of 2.6:1 (elevated feed so easily checked by swapping whips)
A VSWR
test will show up not just an out of tune antenna but stretched/damaged cable and incorrectly installed connectors. We do a VSWR
test as a free service on customer installed equipment so once you installed it, take it into where you bought the gear (if local) and ask if they would mind checking. It really is peace of mind.
I have seen some horrors.
Regards
David
AnswerID:
241140
Reply By: Mike Harding - Sunday, May 20, 2007 at 17:51
Sunday, May 20, 2007 at 17:51
SWR (Standing Wave Ratio or the suitability of the antenna to match to the radio) is a pretty complex area. Whilst any commercial UHF CB antenna will be tuned for minimum SWR at 477MHz (I think that's UHF CB frequency) that is only a theoretical tuning because the designers cannot control the installation conditions and as every installation is different you will, almost certainly, not have an SWR of 1:1 or thereabouts. How far away the match is from ideal is impossible to say without checking with an SWR meter. I suggest you do the installation and make a few on-air checks to see if all is working OK then find a professional installer to do an SWR
test for you - he'll probably charge about $20?
Mike Harding
AnswerID:
241212