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reciving fm using a LP reciver

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LAN_403

803

Mon Sept 20 2010, 12:45AM

Registered Member #2807 Joined: Fri Apr 16 2010, 08:10PM
Location:
Posts: 191

I had a 1980s goldstar fm rado and I was playing the 500,000 watt tranmitter station (95.7). also, I had a 1960s radio with 25 solid state devices. It had AM, HP (high police) LP (low police) and i was listing to the LP, at 32-25 mhz. Amazingly I was hearing 95.7! But, when I turn the goldstar off , the LP doesn't play 95.7 anymore! So, even when the volume is turned off for the goldstar, the Lp radio still plays! So I guess the goldstar is retransmitting the fm radio at around 33 mhz!!!!!!!!!!!!!

wierd, eh?

Adam Munich

Mon Sept 20 2010, 02:05AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

803 wrote ...

I was playing the 500,000 watt tranmitter station (95.7).

Wait what?

Chris Russell

Mon Sept 20 2010, 04:21AM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

Grenadier wrote ...

803 wrote ...

I was playing the 500,000 watt tranmitter station (95.7).

Wait what?

There is a 500kW FM radio station nearby; he was listening to it.

Sounds like a spurious signal for sure. Perhaps the third harmonic of the Goldstar's IF? (10.7Mhz * 3 = 32.1MHz)

Adam Munich

Mon Sept 20 2010, 04:27AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Ahh... I thought he had a 500kW transmitter. Unrelated, I went to an FM radio station myself a while ago just to see how many harmonics I could pick up. I ended up getting 3 on the FM band and one on the VHF band.

But yeah I think Chris hit the nail on the head.

Steve Conner

Mon Sept 20 2010, 08:45AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Sounds like the Goldstar radio is leaking local oscillator.

803

Mon Sept 20 2010, 07:17PM

Registered Member #2807 Joined: Fri Apr 16 2010, 08:10PM
Location:
Posts: 191

Well, the goldstar is around 30 years old! LG was fourmed when 2 korean companies fourmed, lucky and goldstar. The 1960s radio when picking up 95.7, there was alot of static and most of the time the audio was wierd and funny. Does anyone know if the lower police and high police radio band is still used?

PAul

Chris Russell

Mon Sept 20 2010, 08:33PM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

I'm not sure what your radio designates the high police radio band, so I'm not sure if it's still in use. The low band, 32-35MHz is still in use, but not commonly.

These frequencies work better in hilly or mountainous environments than VHF, because the waves are more prone to diffracting around obstacles (VHF is commonly considered line-of-sight only). Their range is also somewhat greater, for the same reason: the waves diffract over the horizon to a greater degree. Unfortunately, there are also some pretty big disadvantages. A 32 MHz antenna is physically much larger than a 155MHz antenna. Also, during years of increased solar activity, the 32MHz band can propagate thousands of miles, which can lead to massive interference problems.

These days, VHF and trunked UHF systems are much more common. These systems are less prone to interference, they're smaller and easier to install, and linking repeaters together to increase range dramatically is not difficult.

803

Tue Sept 21 2010, 07:12PM

Registered Member #2807 Joined: Fri Apr 16 2010, 08:10PM
Location:
Posts: 191

Low- 30- 50 MHZ

High- 147- 174 MHZ

Hope this helps..

I also heard a football station, sounds that are like a atri game, a boring weather man, and ads....

Dave Marshall

Tue Sept 21 2010, 07:51PM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

The low band is indeed in use but only rarely as a primary frequency. More commonly (as in the county I live in) the low band has been relegated to a backup channel in case of repeater failure, massive incident requiring additional frequencies, and for the very most outlying areas with poor Line of Sight to the repeaters.

High band is still used extensively as primary dispatch frequencies through out much of the country, but it's a pretty even split between the VHF 147-174MHz (more specifically, Police/fire/EMS services live between 150-160MHz in the US) and the UHF Mobile Service allocation between 450 and 470MHz.

Newer trunked systems on 450-470, 500ish, and 800ish MHz are starting to gain ground though.

As for what you're hearing, I would think a straight up harmonic from the broadcast radio is unlikely. They would be terribly weak. I would bank on either the Broadcast radio has an IF that is very close to an IF or image on the police radio, or perhaps some other weakness in the design of the police radio is allowing it to hear one of the amplified products of the broadcast radio's down-conversion process. The fact that you're hearing 95.7 on the police scanner even with the volume turned all the way down would point to some very late stage front-end weakness that's leading to overload.

-Dave

803

Tue Sept 21 2010, 08:03PM

Registered Member #2807 Joined: Fri Apr 16 2010, 08:10PM
Location:
Posts: 191

so is it a bad thing?

It doesn't work on other radios, just the goldstar....

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