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27mhz business radio

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KC8EVM

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Quite possibly posting in the wrong forum but here we go anyway as my question concerns LMR as opposed to true Class D Citizens band radio.
I bought (on purpose) on Ebay, a Pace BI-35A base station in the business band portion of 11 meters. This radio is nearly an exact clone of the CB-76 23 channel base station with the exception of instead of a 23 channel selector, it has a 6 position channel selector. I opened it up and it has one set of crystals in position 1 on 27.450 mhz. a quick look inside also revealed a probably 25-40 watt final amplifier with a pretty hefty heat sink mounted on the back of the cabinet. This "CB" business band has always intrigued me but there is precious little information to be found on the net. Im looking for any factual information on both this radio, Pace Pathcom other business rigs, or any first accounts from actual legal users or license holders on this unique slice of spectrum including other manufacturers of 27 mhz type accepted business radios. At first glance my "new" rig appears to be AM. Could that be?

Thanks in advance. Andy
 

ecps92

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4 users in the US on that Freq
http://fjallfoss.fcc.gov/General_Me...ortstring=,+lic_name,+file_num&limit_select=4

Quite possibly posting in the wrong forum but here we go anyway as my question concerns LMR as opposed to true Class D Citizens band radio.
I bought (on purpose) on Ebay, a Pace BI-35A base station in the business band portion of 11 meters. This radio is nearly an exact clone of the CB-76 23 channel base station with the exception of instead of a 23 channel selector, it has a 6 position channel selector. I opened it up and it has one set of crystals in position 1 on 27.450 mhz. a quick look inside also revealed a probably 25-40 watt final amplifier with a pretty hefty heat sink mounted on the back of the cabinet. This "CB" business band has always intrigued me but there is precious little information to be found on the net. Im looking for any factual information on both this radio, Pace Pathcom other business rigs, or any first accounts from actual legal users or license holders on this unique slice of spectrum including other manufacturers of 27 mhz type accepted business radios. At first glance my "new" rig appears to be AM. Could that be?

Thanks in advance. Andy
 

prcguy

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I worked at Pace in the mid 1970s and again in the early 80s repairing and aligning their land mobile products. I believe the BI-35A is AM and should only do about 5w, since they were similar to the US made Pace CBs at that time. Pace had an optional 100W amplifier for that series that usually ended up on CB .

Most of the work I did was on their FM land mobile line and I still have a bunch of manulas and parts for those radios.
prcguy

Quite possibly posting in the wrong forum but here we go anyway as my question concerns LMR as opposed to true Class D Citizens band radio.
I bought (on purpose) on Ebay, a Pace BI-35A base station in the business band portion of 11 meters. This radio is nearly an exact clone of the CB-76 23 channel base station with the exception of instead of a 23 channel selector, it has a 6 position channel selector. I opened it up and it has one set of crystals in position 1 on 27.450 mhz. a quick look inside also revealed a probably 25-40 watt final amplifier with a pretty hefty heat sink mounted on the back of the cabinet. This "CB" business band has always intrigued me but there is precious little information to be found on the net. Im looking for any factual information on both this radio, Pace Pathcom other business rigs, or any first accounts from actual legal users or license holders on this unique slice of spectrum including other manufacturers of 27 mhz type accepted business radios. At first glance my "new" rig appears to be AM. Could that be?

Thanks in advance. Andy
 

cmdrwill

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Way back before the FCC changed the CB service to 40 channels, there was lots of business just above 27.255, the old ch 23 IISRC..

We had two channels at 27.3xx

Prc guy, do you remember Miguel Santana?
 

kf4eyr

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if the radio is crystal controled, it is just a matter of finding the right cyrstals and it can be used on cb,, legality questionable,,,i have seen a lot of the old johnson white faces as they are called that were used as business and forestry radios having their crystals changed out and put on cb channels,,,,
 

KC8EVM

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Thanks to all for the replies,
Further inspection does indeed reveal that it is a 5 watt normal CB PA, and it is also indeed AM. It is basically a Pace 2300 chassis (literally) in a base station enclosure with a power supply and a 6 position switch, with one set of rocks at 27.450. A query of the FCC database revealed 4 active licenses. The fact that it is AM is what most puzzles me as it was my understanding the FCC designated the legal emission on the LMR business frequencies (at that spectrum anyway) as regular old F3 FM voice modulation. So why A3 (AM) transmit and when was it the FCC allowed that?
 

prcguy

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I'm curious if your radio has a big TO-3 case final transistor somewhere in the middle of the circuit board, or a smaller one heat sinked to the chassis? I might have some of the oldest TO-3 finals for those somewhere. Those date back to the early 1970s.

I believe your radio was based on the 2300 or 2376 series CB radio, which was made in Harbor City, CA.
prcguy

Prcguy do you have the service manual for the BI-35A by any chance?
 

JayMojave

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Hello EVM and All: No your in the right place, and great question / subject, a real part of CB radio many years ago.

As I understand there were many Business Band Frequencies / Channels out there, it would be great if someone could post these frequencies. The CB Radio Manufactures sold many of these Business Band (BB) radios for Ma and Pa small business. Everyone wanted a BB Radio as many were 25 watt output and as we all know more power got you got there farther than the 5 watt radios.

The locals in the San Fernando Valley Ca seemed to all want a secret channel they could talk to there buddies on and in secret. Well it wasn't secret as many had tunable ham type radios. But it was a mystique at the time that drove operators on to a "Secret Channel" We had secret channel "X" buts another story.

ECI, Fannon, Pace (as said) and General Radiotelephone made the BB Radios, I am sure there were others. See the site here, all the radios with BB are Business Band Radios.

General Radiotelephone | The Old Tube Radio Archives

Even some of the older AM Marine radios that were 25, 50, or even 100 watt output radios were converted to the CB Band.

On a humorous note here the boys figured out that some radios would get a secret channel by swapping the transmit and receive crystals in the older radios. Well Channel 10 which was a local channel, if the crystals were swapped you ended up on 26.620 MHz which was 455 KHz below channel 10 which is 27.075 Mhz. This frequency is a CAP (Civil Air Patrol) channel and the boys got quit a snotty and unfriendly reply from the CAP guys, telling to get off and never return...... And in some of the General Radiotelephone advertisements in magazines, they showed the radios with a 24 channel capability and using the CAP channel 26.620 Mhz, WOW!

I think in the 23 channel days 22A and 22B were BB channels but not sure, now they are apart of the CB 40 channel set.

The BB frequencies were above channel 23 which is 27.255 Mhz, like 27.420 and 27.450 and I am sure many more. Again someone needs to post these BB frequencies.

Jay in the Great Mojave Desert ..... just down the road ah ways form the fillin station
 

KC4RAF

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Jay, ND5Y in post #5 gave a URL for those frequencies.
The link you gave is interesting. Will have to check it out further. Thanks for sharing.
I also remember back in the days the guys would swap the crystals. Some times they stepped on toes that got them warnings.
Back then, it was a lot more interesting in the CB hobby. Many an operator would tinker around with their radios and learned from their finds and errors! Great days back then...lol
 
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cmdrwill

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ECI, Fannon, Pace (as said) and General Radiotelephone made the BB Radios, I am sure there were others.
E. F. Johnson was one of the largest manufactures that made CB radios, and also a line of Business band radios. Motorola also had a CB and Business band radio line.

Browning Laboratories
International Crystal
and some others I have long forgotten.
 

JayMojave

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Hello All: Yeah good call I missed the #5 post link. Thanks.

Lots of great info here. I may plug some of these frequencies into the scanned and listen in for a while.

Jay in the Great Hot Mojave Desert 102F here today and will get hotter, swap cooler engaged full throttle....
 

KC8EVM

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It appears to use the Motorola MRF8004 final heatsinked on a90 degree piece of aluminum roughly in the center of the chassis. package style looks to be TO-66. Not nearly as big as a TO-3 case. I haven't benched it yet but when I do I'll give you what it does on the IFR. Researching the MRF8004 the spec sheet calls it a 27mhz NPN PO transistor rated at a whopping 3.5 watts.....
 

prcguy

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Ok, at least its not an early 1970s vintage radio with the TO-3 final. I forgot they simply changed the circuit board traces around the transistor for the newer style instead of changing the entire layout. My memory is foggy but it seems like I had the mobile version of your business band radio set up on CB at one time. I also recall having the CB base version and didn't like it for some reason, but that must have been 47 or 48 years ago.
prcguy



\
It appears to use the Motorola MRF8004 final heatsinked on a90 degree piece of aluminum roughly in the center of the chassis. package style looks to be TO-66. Not nearly as big as a TO-3 case. I haven't benched it yet but when I do I'll give you what it does on the IFR. Researching the MRF8004 the spec sheet calls it a 27mhz NPN PO transistor rated at a whopping 3.5 watts.....
 
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