VHF low band

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SIBC
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VHF low band

Post by SIBC »

The Business Radio (UK General) licence, now renamed Business Radio (Simple UK), allows for VHF low band operation (one frequency at 77MHz and four at 86MHz) in addition to frequencies at VHF mid band (164MHz), VHF high band (169MHz and 173MHz) and UHF (449MHz).

Now we have had dicussions on the comparative range of VHF mid/high to UHF.

So, how about the comparative range of VHF mid/high to VHF low?

Has anyone tried this? Would any theoretical advantage of the lower frequency be lost with a short antenna (on a hand-held it would have to be a much smaller fraction of the wavelength thus affecting transmit and receive).

Put simply, which hand-held - VHF mid/high or VHF low - would have the best range with a typical 15cm antenna?

I look forward to the discussion and hope to learn something from it.

Ian Anderson
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Re: VHF low band

Post by Guzzy »

Haven't tried to compare commercial VHF (high) to VHF (low), but experiments carried out with a Yaesu VX-7r, which has the HAM 6m, 2, and 70cm bands, seems to indicate not much difference when used hand-held to hand-held.

The VX-7r has a peculiar antenna though, where the tip is interchangeable for operation on 6m or 2m & 70cm. Perhaps with a proper dedicated hand-held VHF (low) antenna, the performance would be better.

Mobile to mobile with a decent antenna would probably be much better. Don't the bus companies and a lot of Taxi companies use VHF (low) band?

As always, getting a 'proper' antenna above local roof height tends to make a massive difference at VHF/UHF frequencies.
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RogerD
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Re: VHF low band

Post by RogerD »

With some experience with Low and High band PMR, and 2m/4m/6m amateur radio mobile, I can say that the low band gets around rural mildly hilly areas better.

But low band 1/4 waves are unfashionably large on vehicles, and not very efficient on handhelds..... hence why PMR above 139 MHz is far more popular with users needing handhelds.
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Re: VHF low band

Post by asd »

True... Low band is great for distance and hills but poor due to antenna practicalities.

85 - 87.5 MHz (the band used to go to about 87.8 till the mid-90s) used to be a very popular band; very crowded, with several different users heard on most channels. Nowadays there's but a very small fraction of the number of users there was 15 - 20 years ago. The trend in PMR has been to move higher in frequency, and many went over to VHF-Hi band which offers practical sized antennas on handhelds but lesser range.

I remember how well users in the really rural parts of my county used to get out on their simplex low-band channels. Since they switched to VHF-Hi you rarely hear them. It's understandable why they left low-band, as the antennas on their portables (shoulder bag types) were about 6 feet long. But I bet they miss their performance.

EDIT. I don't think I've ever heard any user on the UK Gen low-band channels. (That could largely be due to me using my UBC3500 for RX, which has poor sensitivity down there even on a telescopic antenna). They are very under-used channels and would obviously be ideal for vehicle-vehicle comms, offering a greater range than the other UK Gen channels.
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Re: VHF low band

Post by Hertz »

Experience on 70Mhz, shows that the main factor when it comes to Low band VHF is the antenna counterpoise factor.
On my PYE PFX with the standard rubber duck, which is around 4 times the length of a Puxing or Yaesu VX-7R, the distance is not much different from 2 meters, however following a post several years back on the four meter group website I now use a tail & distance has improved dramatically.
A handheld radio relies on you, the operator, holding it & inductance for it's couterpoise & at 4 meters thats just not good enough, so add a tail of wire, which looks a little silly, but works wonders on performance.
All that is required is a metal screw to the radios chassis, something like a screw that holds the case in place, & sufficient wire to trail onto the ground when held to your mouth, I use around 6 feet, or about 2 meters.
If they tried to change our national anthem would people stand for it?
And ball points....Should we award them?
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Re: VHF low band

Post by BK »

I tried this on 2m and 70cm a while ago. At 70cm the counterpoise didn't really do much as the chassis was already about a quarterwave long anyway, but at 2m it made a huge difference - far more difference than going from a small rubber duck to a quarter wave antenna. I think the importance of a good counterpoise is underestimated, I can imagine what an improvement you'd get on 6m with one (although the antenna would still be a bit impractical). To answer the original question, in my experience the inefficiency of handheld antennas with no counterpoise outweighs the advantage of lower frequencies, you only have to look at handheld CBs to see that.
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iansradios
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Re: VHF low band

Post by iansradios »

Low vhf is better for distance and hilly terrain,thats the reason mountian rescue and army use it as it was extensively tested in all fields.
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Re: VHF low band

Post by bigbloke »

Actually Ian, I think Mountain rescue moved off low band onto VHF highband quite a few years ago now

regards

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Re: VHF low band

Post by iansradios »

low band is still in use,as i supplied some low band kit to a mountain rescue service in scotland last year.not only that but before tetra the highlands and islands council used low band,plus some of the ski slopes,and the mod still use low extensively,,there no one on low band near me yet i pick up low band taxi from over 70 miles away in manchester.
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Re: VHF low band

Post by Hertz »

Taken from the 4 meter forum.
Post Posted: Sun 12 Jul 2009
70.200...120 miles as the crow flies

Posted: Mon 13 Jul 2009
I heard you also (138 miles to Stoke-On-Trent)
Posted: Wed 1 Apr 2009
I have a PFX , and presently run a Wouxun KG-699E on 4 FM (which I find VASTLY superior).
Today I managed my furthest contact yet,
I started hearing Keith at a range of around 58 miles (M6 towards M42) but he was too weak to justify a call at 5w power level my end. Keith was running 30W into a vertical.
by 40 miles (Junction of M42 and M5) he was fully Q5 so I gave him a call and a 2 way QSO was established.
I stopped at Strensham Services later (junction of M5/M50) and could hear Keith quite well on the set top (8 inch) helical. This was at a range of
just under 22 miles. I called him directly on the helical, but wasn't heard.
(hardly surprising!) Wink
If they tried to change our national anthem would people stand for it?
And ball points....Should we award them?
Bob Monkhouse.
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