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Old 24th Mar 2020, 10:44 pm   #1
1955APREN
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Question Analog radio station in Band 3

Today at 12.55Pm etc I had my 625 line tv tuned to the old band 3 ch,s
between the markings on the dial ch 9/ ch10 (206/214 Mcs) I heard about three
radio stations sitting on top of one another fading very quickly . At one point one station came in very clear for a few seconds it was a man talking in English with a
Lady who was Chinese but spoke very good English , she was helping the man to
pronounce words in Chinese.
Does any one know what station this would be and were did it come from.
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Old 24th Mar 2020, 10:52 pm   #2
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Default Re: Analog radio station in Band 3

Is it breakthrough on the 6 MHz IF?
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Old 25th Mar 2020, 12:40 am   #3
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Default Re: Analog radio station in Band 3

That does sound very much like one of the introduction to Chinese sessions that CRI (China Radio International) runs, and they are a very prominent presence on the HF bands nowadays including 49m. It's quite conceivable that a 6MHz FM IF strip with a bandwidth of tens of kHz could demodulate several 49m transmissions at once if AM suppression is less than watertight.
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Old 25th Mar 2020, 1:11 am   #4
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Default Re: Analog radio station in Band 3

49 metre-band breakthrough was a problem with some sets, you would get a service call on the lines of "Radio Moscow in the background". Often affected high rise flats.

My solution was to make a braid-breaker out of two loops of coax and PVC tape.
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Old 25th Mar 2020, 8:24 am   #5
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Default Re: Analog radio station in Band 3

VHF tuners that use the frame grid type RF amp and a pi tuned input circuit have a MW breakthrough coil fitted.
The older style VHF tuners with an RF transformer input do not need the coil. Whether that is the case in this set and that coil is broken or the set design is prone to the problem I donít know.
A really good write up in RC.
https://www.americanradiohistory.com...RC-1965-09.pdf

Appreciate it could still be breakthrough due to poor screening of the 6 Mhz IF strip, still the RC article is worth a read.

Surprise myself on what I sometimes remember, forgot about this problem. A braid breaker is an RF transformer, I used to carry one for TVI problems, can be very effective. It was an engineer from the PO interference service who showed be them in the 60ís.
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Old 25th Mar 2020, 9:58 am   #6
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Default Re: Analog radio station in Band 3

I used to fit AKD braid-breaker in-line filters as part of our 'good neighbour' policy to residents in and around Skelton village to keep our signals (BBC Skelton) out of their tellies.

Then I'd take a look at their telephone junction boxes and clean the corrosion out so they had World Service-free telephones too!
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Old 25th Mar 2020, 5:22 pm   #7
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Default Re: Analog radio station in Band 3

Quote:
Originally Posted by russell_w_b View Post

Then I'd take a look at their telephone junction boxes and clean the corrosion out so they had World Service-free telephones too!

As a favour, to someone near the station, I once used a spare ADSL filter to keep Moorside Edge out of their Panasonic fax/phone.
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Old 25th Mar 2020, 6:24 pm   #8
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Default Re: Analog radio station in Band 3

As a kid, I lived for a while in the fishing village of Hopeman, just a long spit from the Burghead senders- R3 MW could be heard faintly in the background of most things. In that way of RF, I think that the R3 sender was actually the lowest power amongst the BBC cluster.

I wonder if 405 line tellies ever suffered from the "colourful" fish-fone repartee in their AM sound channels, or even radio amateur traffic? Perhaps older chassis-type construction would offer better immunity than PCBs under nothing more than hardboard.
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Old 25th Mar 2020, 9:21 pm   #9
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Default Re: Analog radio station in Band 3

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Originally Posted by turretslug View Post

I wonder if 405 line tellies ever suffered from the "colourful" fish-fone repartee in their AM sound channels, or even radio amateur traffic? .
There was plenty of low-VHF AM about. Taxi drivers might have used colourful language occasionally. My dad used to like to listen to the M2CK police messages that came in loud & clear on Ch10, but only when ITV Winter Hill on Ch9 had closed down for the night.
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Old 25th Mar 2020, 9:28 pm   #10
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Default Re: Analog radio station in Band 3

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Originally Posted by rambo1152 View Post

There was plenty of low-VHF AM about. Taxi drivers might have used colourful language occasionally.
I once picked up some 'colourful' taxi-talk on my cassette player when I was following a taxi through Workington!

Quote:
Originally Posted by turretslug View Post
I think that the R3 sender was actually the lowest power amongst the BBC cluster.
Just picking at nits here... 'Senders' were HF for broadcasting overseas. Burghead had transmitters.

I know...
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Old 25th Mar 2020, 10:32 pm   #11
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Default Re: Analog radio station in Band 3

Bit more nit-picking: two very different mechanisams involved
'Transmitters' got into the sound by cross-modulation of the front end and I expect would be clean audio and present only when tuned to a local TV signal (and probably would modulate the video as well)
6MHz 'Senders' get there by leaking into the inter-carrier (FM) sound IF and would be clipped and distorted. The latter is only possible with a Dual Standard set
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Old 26th Mar 2020, 1:20 am   #12
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Default Re: Analog radio station in Band 3

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Originally Posted by Julesomega View Post
6MHz 'Senders' get there by leaking into the inter-carrier (FM) sound IF and would be clipped and distorted. The latter is only possible with a Dual Standard set
Why not also single standard sets? (625 line only, in this context).

These TV IF's and FM discriminators were often badly implemented, particularly in the valve era. The 6MHz AM interference was faint, but perfectly clear.
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