BC III - DIY Bearcat III Antenna

[flickerfly]

Is it possible to rig together a simple antenna for a BearCat III using scrap wire, etc.? I was given this scanner without an antenna or power cable. I was able to wire it up to an old PC power supply. I'm getting lots of static on all the channels and some sound rhythmic enough to make me wonder if it might by voice, but I guess with no antenna attached, I'm not likely to pick up much.

I did jam a wire into the center of the external antenna and definitely got louder static.

 

[krd400]

In order to pick up any voice transmissions on this antique radio, the crystals must be programmed to an available frequency in the Colorado Springs area. Do you happen to know what frequencies are configured into the crystals? On top of that you will only be able to pick up analog frequencies. My guess is that most if not all the agencies that were configured on the crystals have gone to digital. Sticking a wire into the antenna connector probably only increased the static of a dead frequency. Good luck.

 

[flythunderbird]

In order to pick up any voice transmissions on this antique radio, the crystals must be programmed to an available frequency in the Colorado Springs area.

Uh, you can't program crystals ...

 

[ofd8001]

Brings back memories of so many years ago - my very first scanner!

You could use the same type of antenna (mobile or outside) as any other scanner. All you need to do is cut the connector off, strip the coax and solder on a Motorola type car radio antenna plug. That in turn plugs into the external antenna jack on the rear of the scanner.

Of course with so many radio systems being trunked and/or digital nowadays, there may not be much the scanner receives. Still you could determine if there are conventional/analog frequencies in use in your area and then do a Google search for the crystals for these frequencies.

In answer to the question, yes you can just shove a wire into the rear jack and might be able to hear something, but that may not be very effective.

 

[popnokick]

Once you get crystals for the freqs you need, you can make this antenna easily out of scrap wire and a cheap TV 75 to 300 ohm transformer. Scroll down the wiki article to the "wire version" of the antenna. Put the Motorola-type car radio plug (pic in this thread) on the end of the 75 ohm cable that goes into the scanner.
Homebrewed Off-Center Fed Dipole - The RadioReference Wiki
And as was noted, this is an analog scanner that is not going to receive the digital transmissions likely to be used in your area. So pick crystals for freqs that are known to be analog. Look in the RR db for the freqs in your area. Don't be surprised if it comes down to NOAA transmissions, railroad, ham radio, FRS/GMRS, and little else.

 

[kruser]

Uh, you can't program crystals ...

Sure you can! It's called cutting or grinding

Not saying the average Joe could do it though and you are correct as it is not really programming. At least they never called it that back in the day they were popular for scanners.

Old hams called it "cut a new rock" when they made their own.

At one time, there was a company that sold a form of tunable crystal. It was just a tunable oscillator that plugged into a crystal socket. I never had one and they were not sold for long so I assume the cost was way high or they did not work worth a darn or too hard for the average person to wire in as I'm sure they would have also needed a steady regulated power source.

I recall seeing them listed in the tiny ads in the back pages of Poplular Electronics magazine as well as whatever scanning magazines there were back in those days.

 

[kruser]

Brings back memories of so many years ago - my very first scanner!

Was the pictured BC-III yours? It looks like it was modified to use a 203 Hz PL tone judging by the sticker by the external speaker jack.

I never did add PL capability to any of mine as I mostly used them for railroad use. I still have several of them running today on the rail band as well as one setup for VHF Low band that still monitors Missouri's low band highway patrol. Yes, the state still uses the low band system for those areas the new VHF High band P25 sites do not reach. They use up to 5K watt transmitters and brute force the low band signal through the hills of the Ozarks.
They knew this when they installed the statewide P25 system so they planned on keeping the low band system licensed and operational.
Not sure about the northern parts of the state where the land is pretty flat but I'd guess low band use is pretty rare in those parts.

The old BC III's worked well and had great audio for the old low band system!
We also still have a lot of analog in use in the state so I'll pop in crystals for some of the local stuff just for fun.

 

[kc2kth]

Wow, what a classic radio. I'm sure you can find an actual antenna for that if you look around a bit. It would in my opinion add to what is a fine collector piece. I'm biased though as this was the scanner I first saw as my grandmother had one in her kitchen that my uncle had bought and left when he moved out. My parents bought themselves the next model up, the Bearcat IV. I'm not sure where that radio went or the BCIII, but I wish I had them today.

 

[ofd8001]

Kruser-
Nah, just a picture I found on Google images. I needed to confirm my memory that the speaker had an antenna jack on the rear and what type it was.

Kc2kth-
Yeah, I wouldn't mind having my old one back. The only thing I didn't like about the scanner was you had to choose which two of the three bands - VHF low, VHF hight and UHF. It would not do all three. Still a great scanner in its day. I remember making side trip to the Electra place in Indianapolis to get some crystals and a quick repair, which they did right away for me.

 

[kc2kth]

Kc2kth-
Yeah, I wouldn't mind having my old one back. The only thing I didn't like about the scanner was you had to choose which two of the three bands - VHF low, VHF hight and UHF. It would not do all three. Still a great scanner in its day. I remember making side trip to the Electra place in Indianapolis to get some crystals and a quick repair, which they did right away for me.

I didn't realize you couldn't use all three simultaneously. I knew the IV added UHF capabilities, but to this day I don't believe that town (Saratoga NY) has anything above VHF so it never was an issue in my case.

 

[ofd8001]

I believe the main difference between the III and IV was that the IV would do all three bands along with having a silver facepiece.

With the III, there were separate boards for VHF low, VHF high and UHF. They were attached to another board on the scanner and you had to insert crystals in a certain way depending upon band.

When these scanners made their appearance in the 70's, UHF was kind of new. Most jurisdictions were using VHF low or VHF high.

I did a Google search and was able to find the manual for the Bearcat III if you are interested:

http://www.google.com/url?sa=t&rct=...OTTp7pDI3DJkh3uvGy8DsUw&bvm=bv.69837884,d.b2k

 

[johnnyelectron]

The manual cuts off right where it shows the power plugs for 120VAC and 12VDC. Does anybody have the correct plug/socket configuration for the 4 pin plug on the back of the Bearcat III ? Thanks.

 

[pro92b]

Power connector schematic

 

[parnass]

The manual cuts off right where it shows the power plugs for 120VAC and 12VDC. Does anybody have the correct plug/socket configuration for the 4 pin plug on the back of the Bearcat III ? Thanks.

The BCIII uses the same power connector as the BC IV, Bearcat 12, etc. Here is the pin configuration for the BC IV.

 

[johnnyelectron]

Thanks