SSB Radios IF Filters Too Narrow for AM Receive

[Flash Gordon]

Has anyone experienced poor sound quality from their AM/SSB CB radios, in the AM receive mode, and having to tune the clarifier to one side or the other to clean up the received signal?

I am seeing the problem on older 23 and 40 channel AM/SSB CB radios with 7.8 mHz IF. Seems to me that the crystal filter, a rectangular block 36mm x 22mm x 20 mm, located in the center of the dynascan circuit board series PC-196(**), is too narrow for AM receive.

I came up with a mod that routes the 7.8 mHz IF RX signal bypassing the filter. This is controlable via a switch that controls a diode to pass the signal. The results are remarkable. You get a more fuller audio spectrum, and listening for long periods is less taxing. The problem with this mod is that selectivity goes out the window. I live out in the sticks so this is not a problem for me. I do this mod only on the base station models, as they have two 7.8 mHz filters (the large one and a smaller one that looks like a regular crystal with 3 pins.).

My question for the Forum is this: Are there 7.8 mHz crystal filters available with a wider bandwidth? Something similar to an AM filter for the Yaesu FT-101 series, but at 7.8 mHz. I bought an AM filter from Fox Tango years ago. It made a big difference.

Any ideas out there?

[Slowdraw]

All of the ssb 7.8 mhz filters I remember were 6 khz, just wide enough for am, and just narrow enough for good ssb. You probably won't find a 10 khz filter for AM use, but I always thought the filter used in the cobra 148 was the best.

Never had complaints about am reception with them. The filter had a smooth and broad response with none of the peaks and valleys that causes the problems you are describing.

It is also possible that the radio you've got is misaligned, which could cause a similar complaint.

[316]

He's right the Cobra 148 filter does a great job.

[DX47]

What filter is used in most of the rigs made these days? AM and SSB sharing the same filter?