Bandspread on CB Board

Denstar51 · Post by **Denstar51** » Saturday 8th Mar 2008, 1:17

I wanted to ask the group if after adding more channels to the cb
board PTBM036AOX, can the board cover the band spread. The
coverage in question is about 1.6Mhz on both transmit and receive.
Would this board have to be broadbanded? Zodiac suggested I post
this msg. to the group.

Thanks

Denstar51

Rick · Post by **Rick** » Saturday 8th Mar 2008, 10:19

You will need to change some cap and transistor to get peak performance over 1.6 MHz, but you should be able going up from the CB band by about 350 to 400 KHz and down by about 200 to 300 KHz, with out changing any components.

It would be a good idea to change C164 in the RX strip from 2pF to 3 or 4pF, and C139 in the TX strip from 2pF to 3pF but if you remove C601 1pF then change C139 to 4pF and change C140 from 2pF to 3pF.
Re-align all coils on the part of the band you are using but do not adjust L110.
Hope this helps. Let us know how you get on.

Denstar51 · Post by **Denstar51** » Saturday 8th Mar 2008, 10:43

Thanks, Rick, Zodiac said you're good with replies and great with tech
know how.

Dennis [/b]

Denstar51 · Post by **Denstar51** » Saturday 8th Mar 2008, 10:58

Rick

You mentioned transistors. What transistors?

Denstar51

Rick · Post by **Rick** » Saturday 8th Mar 2008, 21:49

The front end and 1st mixer transistors and any 2SC710 which is a noise transistor.

Denstar51 · Post by **Denstar51** » Sunday 9th Mar 2008, 2:18

Ok, Rick, but what transistors should be used in their place?

Rick · Post by **Rick** » Sunday 9th Mar 2008, 9:46

Q114 front end change to 2SC1674 or better still 2SC2999, Q110, Q115, Q116, Q118, and Q119 change to 2SC1675, and change diodes D109 and D110 to 1N6263 Schottky diodes.

You may also have a problem with the VCO not locking, if you do change D101 to BB809 or SVC251 and up the value of C101 22 to 27pF if needed but try to stay with the original cap and just change the varicap diode, if you do change the cap keep it under 27pF.

There are lot of improvements could be make to the chassis, but what I have told you should get you the bandwidth you need.

Denstar51 · Post by **Denstar51** » Saturday 21st Jun 2008, 0:53

I'm waiting on parts for that Ptbm036AOX board, Rick, but I wanted to know what board model that is on the the schematic you posted on cb tricks for the Ham International Puma, the one that is drawn white on blue.

Denstar51

Rick · Post by **Rick** » Sunday 22nd Jun 2008, 3:59

The Ham International Puma schematic on CBTricks is PTBM049AOX.
http://www.cbtricks.com/radios/ham_inte ... /index.htm

Denstar51 · Post by **Denstar51** » Sunday 22nd Jun 2008, 7:18

Thanks, Rick...I thought It might be. Do you have a copy of the PTBM092cox
board with the PTZZ033AOX board on it?

Rick · Post by **Rick** » Sunday 22nd Jun 2008, 22:00

No I do not have the PTBM092COX Sch.

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