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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 5th Aug 2022, 10:58 am   #1
its ur aerial
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Default 2M Mobile 7/8 Whip.

I have just restored my old 7/8 2M Whip, from when I first got my ticket back in 1981.
Accepting that 2M is not a hive of activity these days, but why did the 7/8 whip that was so common, fall out of favour.

Ken, G6HZG.
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Old 5th Aug 2022, 3:44 pm   #2
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Default Re: 2M Mobile 7/8 Whip.

A 7/8 wave needs a phasing coil somewhere along its length as well as a base matching coil/network so it becomes visually unattractive as well as unwieldy and tending to bend over to sub-optimal angles when you're driving at Motorway or Autobahn speeds...

I have only ever used 1/4 or 5/8 wave antennas on 2M, any lower gain being easy to offset by improving the transmitter (my first 2M mobile radio was a Pye Vanguard which happily put out 60 Watts, and with a grounded gate U310 FET preamp I never had problems hearing people either).
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Old 5th Aug 2022, 4:41 pm   #3
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Default Re: 2M Mobile 7/8 Whip.

I must admit, living in a very rural area, it does catch on the bushes and trees, and is a bit unwieldy, but we do not have any Motorways, only about a mile and a half of Dual carriageway, so the bending is not a issue here.
Up until this was given another lease of life I had been using a 5/8 wave for some years, and I can't honestly say I had not noticed any real difference in performance, possibly the noise level on the 7/8 whip is better.

Ken, G6HZG.
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Old 5th Aug 2022, 7:57 pm   #4
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Default Re: 2M Mobile 7/8 Whip.

The vertical radiation pattern from a 7/8 whip must be quite narrow, so I would think rapid fading on weak signals as the whip moved around must have been a problem at times. We had a similar issue on motorway police cars using thin 1/4 wave whips on 80MHz in the 70s when travelling at speed. I once drove up the M6 at 100mph to test the theory, escorted by a marked police car!

Martin
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Old 6th Aug 2022, 6:34 am   #5
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Talking Re: 2M Mobile 7/8 Whip.

That sounds like fun

Ken G6HZG.
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Old 6th Aug 2022, 2:30 pm   #6
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Default Re: 2M Mobile 7/8 Whip.

Cosmetics are important - a 5/8 or 7/8 wave 2M whip on the roof of a small car can make it look like a fairground dodgem-car.

In my mobile radio days I would only put quarter wave high band whips on the roof of a car , 5/8 wave antennas and low band quarterwaves went on the rear wing or sometimes on the flat panel where the rear wing the rear window and the boot opening met. This was great when using boot mounted radios.

The other big problem with long antennas mounted high on a vehicle is their tendency to be damaged when using garages or multi storey car parks. People would forget about the antenna on the roof until it was too late...
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