Radio Shack TRC-57 and Teaberry Stalker 2 Mirror images

[tinkyr]

Hello all

About 7 years ago there was a thread on this site that I participated in about the Pearce Simpson Simba SSB/2. There is a lack of information about that radio, and people were asking questions. At the same time, I was interested in a restoration project and I picked that radio. I was feeling nostalgic and I wanted a radio that had the vibe of the 1970s but could be used as a modern 40 channel radio without ruining its stock looks. It is worth looking at What Was The Pearce Simpson Simba SSB/2?

Anyway, as a result of that youtube video, I got a lot of inquiries about doing the same for others, and also doing the same to other radios. I thought about it a while, and I decided I might try to make a universal board and then the type of radio to install it in would be selected with a DIP switch. When I did the original project, I had two runner ups, those were the Teaberry Stalker 2 and the Radio Shack TRC-57. I acquired the Sams Photofacts for both of them, and my memories were confirmed, that they were basically the same radio. They are schematically almost identical. I was used to this. Of course many different radios from different manufacturers use the same PCB. Then I noticed something odd. The boards are indeed similar, but they are almost MIRROR IMAGES of each other!

This seems astonishing to me. I am wondering if this was new to me and old knowledge. I have provided some pictures.

First, we have the radios side by side


Then we have just the PCBs


So now, I have intentionally created a mirror image of the board on the right below. Look at the similarities.
The board layouts are virtually identical when viewed as a mirror image. The only section that differs it the section outlined below in red. Even with the different layout, the schematics for that section are almost identical. Look at the location of the relay, the tunable inductors, the audio chip, the final and driver, the PLL Module, the big capacitors, the round ICs, the crystal filter, the rectangular notch in each board in the upper left corner. It is a mirror image!




Has anybody ever noticed this before? Does anybody have a clue as to why somebody would go to the bother to do this?

By the way, I looked at the board for the Teaberry Stalker 1 mobile, and it has the same board as the Stalker 2. It is reminiscent of the same Uniden 858 boards in the 40 channel Stalker 202 base and the Stalker 101 mobile

Any theories?

 

[trentbob]

Theories? A lot of stuff was rebranded then and they shared from Radio to radio. Old equipment LOL.

 

[cralt]

Is it the same board just populated upsidedown?

 

[RFI-EMI-GUY]

The tools used for board layouts back then were photographic. So it is possible the designer decided to flip it over and cut and paste for a new model.

 

[tinkyr]

Theories? A lot of stuff was rebranded then and they shared from Radio to radio. Old equipment LOL.

I know there were PCBs that were installed in many different radios. For a while it seemed like every manufacturer had some version of the PLL02A PCB. Of course my favorite, the UPD858 chassis that was in the TRC-449 was in several radios by different manufacturers. The point here is that hsi was not the same board. It is a mirror image.

 

[tinkyr]

The tools used for board layouts back then were photographic. So it is possible the designer decided to flip it over and cut and paste for a new model.

Well, this upside down theory makes the most sense so far, but things like the relay, the ICs, and all the metal transformer cans would not work upside down unless they installed them on the underside. I am not sure why they would think they needed to go to all the work of making a mirror image to have a new model. As has been mentioned, exact boards were used in different models, and continue to do so to this day. I wish we could set up an interview with a senior person at Undien and ask them a few questions. I would really like to know, for example, if they really got pressure from the FCC to stop manufacturing the 858 chassis, or if that is an urban legend.

 

[trentbob]

You are stretching my brain way beyond capacity LOL the 449, 457 and 458 differ in small ways from other brands like Cobra, President, Robyn and Teaberry that used the 858 Uniden chassis.

There was slight differences in the wiring of the 449 that gave it terrible adjacent Channel rejection.

Kind of funny that I haven't thought about this as I would have no reason to in a long time and I smell an odd odor of wood burning in my brain LOL.

 

[tramd]

The reason the TRC 449, the Cobra 138XLR and a few others that used those boards had poor rejection was that they lacked L6 and FT2. They used a jumper in place of those two parts. If the transformer and filter are installed they will be the same as the bases with much better side channel rejection.

 

[tinkyr]

You are stretching my brain way beyond capacity LOL the 449, 457 and 458 differ in small ways from other brands like Cobra, President, Robyn and Teaberry that used the 858 Uniden chassis.

There was slight differences in the wiring of the 449 that gave it terrible adjacent Channel rejection.

Kind of funny that I haven't thought about this as I would have no reason to in a long time and I smell an odd odor of wood burning in my brain LOL.

Yeah, they do differ in some ways, but they all started out with the same PCB. Some got stuffed with different parts, or in the case of some Radio Shack versions whole inductors were bypassed allegedly to save on cost. The point is that they started with the same PCB. In this case, the boards are almost electrically identical, but mirror images. It just seem like a lot of work for no reason, and boards were a lot harder to layout back then.