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SWR across uk & cept frequencies
Topic Started: Thursday, 2. August 2018, 18:05 (225 Views)
Goat
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26 Charlie Tango 3106

Hi all,

Can I ask whether I should be expecting significantly higher SWR readings over the cept block in comparison to the UK block?
I'm using a magmount with a 1.55m orbitor & get SWR between 1.2 & 1.5 on the UK frequencies and 2.1 & 2.7 on the mid block.
I've tried umpteen combinations of position & antenna length, but up to press these are the best readings I can get. Due to having a profiled roof I cannot get a central location with full contact of the magmount base, but I can if I position the antenna about 1/4 distance from the front. This is where I get the lowest readings as above.

Is it going to be a compromise across both bands - or do I need to buy myself a new motor with a flat roof ????

Many thanks

Gary
26ct3106
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G1XGM
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you should SWR It in on channel 40 of The CEPT band.This is roughly half way between The 2 bands.UK Band 27.60125-2799125.CEPT 26965-27405.The perfect frequency for SWR'ing would be 27.485.But This is not possible.
Edited by G1XGM, Friday, 3. August 2018, 11:19.
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roundtower
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26 Charlie Tango 2817

Goat
Thursday, 2. August 2018, 18:05
Is it going to be a compromise across both bands - or do I need to buy myself a new motor with a flat roof ????
You may well have to accept, tuning for lowest SWR between the two bands, that on Ch 1 CEPT and Ch 40 UK you've got an SWR of 2:1. Or else you have to decide which extreme of either band you're prepared to sacrifice to achieve a better match elsewhere. While changing the mount might improve things a bit, the truth is that with relatively short loaded mobile aerials there will nearly always be that sort of compromise to make.
-------------------
TC62 26CT2817
Yaesu FT-891 CRT SS7900 Harvard H-404 Uniden 400 Icom ICR-75 Amstrad CB901 President Grant Baofeng UV-5R KW Electronics KW202
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Northern Crusader
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26 Charlie Tango 1760

Antennas have three properties, bandwidth, efficiency and size and you can have any two of those you want and the third will be what you have to compromise.

If you want a small size and efficiency it will mean a narrow bandwidth such as you're achieving.

If you want small size and wide bandwidth you sacrifice efficiency, a dummy load being the ultimate example.

If you want bandwidth and efficiency it'll mean you have to have a large antenna.

If you want an antenna that covers both all of CEPT and UK below 2:1 you need to be looking at a Sirio Performer 5000 but note that it is 1.95m long with a thick whip.
26CT1760 / M0GVZ
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Nik Gnashers
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26 Charlie Tango 573

Brilliant advice given.

Do you know anyone with a SirioHP4000 you can try ?
Even one that is tuned for a different vehicle may show a better swr reading over a wider frequency range than your present antenna ?
M6GFT ::: QRZ Page- http://www.qrz.com/db/M6GFT
[imgw=150]http://i.imgur.com/RJjZCOw.jpg[/imgw]
All CT members are expected to use good operating procedure, good manners, and be friendly...Please do not chat on any calling frequencies, or use bad language on air, thank you it is appreciated.
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Gunrunner
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I use the sirio 4000hp and the 5000 turbo and the 800 performer and the swr over uk 40 and mid bands
is very good, the bigger the antenna the more chances of getting a good swr of both bands and with mine they go to 25mhx and up to 30mhz,
yes the swr goes up at each end but 1.5 is still usable but on mids 1.3 and uk40 1.2 , there all good antennas but the smaller,
the antenna the les chances you have of getting a good swr over the uk40s and mid bands, I hope what ever you using you get a good swr,
:cheers: :pirate2:
Never go faster then your guardian angel can fly
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Goat
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26 Charlie Tango 3106

Thank you for your time and advice folks, much appreciated.
A little more time to be spent fettling things me thinks.

Someone could have suggested a new car though... ;-)

Cheers
Gary
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Captain Kirk
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26 Charlie Tango 013
I'm using a President Missouri mag mount 72cm long swr is 1.7 ch40 UK and 1.8 ch1 EU, RX is good does me for local but you need a longer twig for DX.
Captain Kirk-John 26CT013/26TM013 mobile South Cheshire 14 AM 27.125mhz
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