UHF AM users

Scanning radio frequencies for the East Midlands
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Wyndham
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UHF AM users

Post by Wyndham » 07 Sep 2012, 16:27

I was searching round the UHF band and found a few local AM users on the following frequencies:

455.0875
455.6625
456.9250

They appear to be connected to shopwatch, but further monitoring is required.

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RogerD
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Re: UHF AM users

Post by RogerD » 07 Sep 2012, 18:18

Are you sure it's not coming through from FM transmissions via 'slope detection'?
Try NFM, tuning around those frequencies in 5 or 6.25 kHz steps?

455MHz in particular is usually used with 6.25kHz offsets from what people regard as standard 12.5kHz spacings.

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Minus1
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Re: UHF AM users

Post by Minus1 » 07 Sep 2012, 20:07

"455.0875" could be either 455.0625 (50k bandwidth, but you can hear it with 25k set, used by commercial radio stations for outside broadcast car to studio link) "Free Radio" in Birmingham use it for example (amongst other freqs).

or 455.09375 a JFMG channel (NFM) used by Sky Sports (and possibly others at times).

It certainly won't be a genuine shopwatch frequency, maybe you are getting a ghost of another frequency entirely.


455.6625 is not allocated (it was a railway "cab secure radio" freq)
455.65 is used at East Mids Airport


At least 456.925 sounds a valid freq for Shopwatch, but it won't be AM.

AFAIK, the only uses of AM at UHF are military aircraft.

If you try and listen to an FM transmission in AM you will hear distorted audio.
KEY : = channel/stud | ~ = CTCSS/DCS | ^ = transmitter site | ¯ = overhead | * = trunked

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Wyndham
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Re: UHF AM users

Post by Wyndham » 07 Sep 2012, 22:23

I put them into a scanbank with my existing NFM shopwatch frequencies and the audio was the same, although in one case the audio was better than the FM channel.

One frequency was offset by 750kHz, another by 900kHz, but the other was over 5MHz.

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Minus1
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Re: UHF AM users

Post by Minus1 » 08 Sep 2012, 08:55

How close are you to your shopwatch user(s), what is their actual freq, and what scanner are you using?
KEY : = channel/stud | ~ = CTCSS/DCS | ^ = transmitter site | ¯ = overhead | * = trunked

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M0MTH
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Re: UHF AM users

Post by M0MTH » 08 Sep 2012, 09:19

seriously doubt there are any users on AM around the frequencies you listed, fairly sure it's only really civil & mil air on AM these days?

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Wyndham
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Re: UHF AM users

Post by Wyndham » 08 Sep 2012, 13:22

Minus1 wrote:How close are you to your shopwatch user(s), what is their actual freq, and what scanner are you using?
They're probably around 0.5 miles as the crow flies...on these freqs
455.8375
456.7500
462.2500

I'm using an AR8200

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Re: UHF AM users

Post by scanhermit » 05 Mar 2014, 18:06

I heard 449.4125Mhz on Am today, at Watford Gap services. I was scanning in FM and it stopped on that frequency but all I got was a crackle. I switched to AM and the voices came through clearly. I think one or more of them were mobile.

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Re: UHF AM users

Post by radtech » 05 Mar 2014, 20:34

Where can one purchase a UHF AM business radio?

Answer: You can't.
Rich

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Re: UHF AM users

Post by Adriano9966 » 05 Mar 2014, 20:38

:) It would be nice to have some usage of AM on 70cms or two metres .Every now and then I can work a few stations on 29mhz AM ;)

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Re: UHF AM users

Post by Gemini4 » 05 Mar 2014, 22:51

am on uhf now theres something new :) :lol:
try scanning in 12.5 steps NFM because i pick up the cameras in Derby and hear no such thing,sometimes
you can hear the music in the shop when a caller gets in touch with the camera team.

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Re: UHF AM users

Post by scanhermit » 06 Mar 2014, 15:05

radtech wrote:Where can one purchase a UHF AM business radio?

Answer: You can't.
My PSR295 only does 12.5Khz steps in the 400's, so I suspect that the explanation is as above - they were on NFM and I had to use AM to hear 'em.

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