totally baffled ...help needed please

The place to talk about specific amateur radio equipment and all types of accessories, fixes, repairs and modification.
Post Reply
User avatar
NITRO
Super Member
Super Member
Posts: 473
Joined: 23 Apr 2011, 13:15
Location: Newport S.Wales

totally baffled ...help needed please

Post by NITRO »

i put up a home made inverted v antenna using thin stainless steel wire i had..for the 40 meter band..... the atu on the radio , yeasu FT450AT got the swr down a litle more and i got some great contacts on it... last night my mate came round with his swr meter and checked how low it actually was ... it was high ... over 2.5 :o ... we tried to adjust the swr by moving the ends in 2 inches at a time , but after over 2 foot later we put it back to the origional position and lengthened it 2 inches at a time up to 2 foot ... no difference whatsoever ...
we called it a night and decided to changre the wires for multi stranded, plastic coated ..... this morning i took the antenna down and measured the lengths out to 35 foot exactly each side ( start long and work in .....)
6 hours later... after shortening the ends 3 inches at a time ... STILL the swr's well over 2 even tho we shortened it right back to 32 foot :crazy:
took it down , re soldered and checked all connections twice and the thing just wont drop on the the swr ....... {bnghd}
i can receive brilliantly on it ( and 40 was banging all day here today ... typical ahhh :yawn: )
anyone any ideas on what the hecks going on with it ??
thanks
163-TM-565
User avatar
Tigersaw
Radio Addict
Radio Addict
Posts: 895
Joined: 19 Oct 2013, 15:48
Call Sign: GW6RRL
Location: Llanwrtyd Wells Powys
Contact:

Re: totally baffled ...help needed please

Post by Tigersaw »

When your antenna is resonant it doesn't mean its matched to 50 ohms. In fact a low swr isn't always an indication of a good antenna. You need to put an analyser on it to see whats going on.
If you really need to see a low VSWR, then try a 1:1 balun at the feed point, insert a common mode choke at a convenient place, try altering just one leg a bit at a time in case of imbalance etc.
Diesel man
Regular
Regular
Posts: 36
Joined: 30 Sep 2015, 04:35
Call Sign: 121

Re: totally baffled ...help needed please

Post by Diesel man »

Vswr at 2 is not bad the fact the ATU tunes it you worked on it and it receives fine I'd leave it.
User avatar
kr0ne
Veteran
Veteran
Posts: 4536
Joined: 25 Sep 2011, 18:33

Re: totally baffled ...help needed please

Post by kr0ne »

And if you're absolutely determined to lower the SWR measured at the back of your radio, lenthening the coax by 30 metres or so is probably the easiest way... ;)

(There is a real point behind the above statement, if you can see through the facetious sarcasm...)
User avatar
Unit 148 Mobile
Super Member
Super Member
Posts: 125
Joined: 24 Sep 2010, 20:50
Call Sign: G4ZOW
Location: Limassol, Cyprus
Contact:

Re: totally baffled ...help needed please

Post by Unit 148 Mobile »

1. Tune the antenna to resonance.

2. Use the ATU to match it's impedance to 50 ohms.

Unit 148 Mobile.
Post Reply