Hi gang,
I'm looking for any information regarding converting pll type cbs to 10m.
Specifically I picked up a couple of Cobra HH33 handhelds and it looks like
a simple reference oscillator xtal change along with a new 2nd oscillator
using the orignal pll rock will get these things somewhere on 10.
Ideas? Web sites? Books?

Thanks!

Bob

"Bob" wrote in message
. ..
Hi gang,
I'm looking for any information regarding converting pll type cbs to 10m.
Specifically I picked up a couple of Cobra HH33 handhelds and it looks
like a simple reference oscillator xtal change along with a new 2nd
oscillator using the orignal pll rock will get these things somewhere on
10.
Ideas? Web sites? Books?

Thanks!

Bob


Years ago (probably in the 70s), there was a flood of CB chassis on the
surplus market from Hy-Gain, a major manufacturer that was going out of
business. There was a number of magazine articles in 73 Magazine that went
into excruciating detail on the CB-10M conversion. I never did one, but as
I remember, it was a matter of changing crystals and some minor retuning.
Don't remember if there were any component changes necessary, but if there
were, they would likely be in the tuned RF circuits in the receiver
front-end and in the transmitter final stage.
Take a look here (http://www.cbcintl.com/pllbook.htm) and you should get a
pretty good idea on how to do your radio. If your Cobra is a recent model,
the PLL might be completely different than the old PLL02 chips, but the
theory should still be the same. There's also a doc on CB to 6M conversion
at
http://6mt.com/index.php?option=com_... 21&Itemid=53.
First thing I could recommend would be to see if you can find a schematic
for your radio. That would allow you to do the math on the crystals and how
they mix to make it work.

Cheers,
--
Dave M
masondg44 at comcast dot net

One good thing about Alzheimer's; you get to meet new people every day.

"Dave M" wrote in message
...

"Bob" wrote in message
. ..
Hi gang,
I'm looking for any information regarding converting pll type cbs to
10m. Specifically I picked up a couple of Cobra HH33 handhelds and it
looks like a simple reference oscillator xtal change along with a new
2nd oscillator using the orignal pll rock will get
?? these things somewhere on 10.
Ideas? Web sites? Books?

Changing the reference oscillator will change the channel spacing so
be careful here if you want the 10 meter channels to be 10 kHz apart.

Years ago (probably in the 70s), there was a flood of CB chassis on the
surplus market from Hy-Gain, a major manufacturer that was going out of
business. There was a number of magazine articles in 73 Magazine that
went into excruciating detail on the CB-10M conversion. I never did
one, but as I remember, it was a matter of changing crystals and some
minor retuning. Don't remember if there were any component changes
necessary, but if there were, they would likely be in the tuned RF
circuits in the receiver front-end and in the transmitter final stage.

I remember these. They were pretty trivial to convert to ham use.
Actually almost all of the CB radios of that time period used
identical circuit boards - except for the Tandy/Radio Shack models.
In radios with an automatic noise limiter or noise blanker, for
example, they just stuffed in a few more parts on the same printed
circuit board. I remember taking the covers off a $600 rack-mounted
radio (Dak) and showing the disappointed owner that inside it was
identical to a $39 radio!

One local club even built a 10 meter repeater. Since it is
relatively trivial to add FM to a transmitter, the repeater was FM-IN
and AM-OUT. Those Hy-Gain/Uniden/Cobra/Midland/etc. radios were
used with a varactor diode added to the transmit chain. The repeater
used separate sites for the receiver and the transmitter instead of a
duplexer. It worked quite well.

Take a look here (http://www.cbcintl.com/pllbook.htm) and you should
get a pretty good idea on how to do your radio. If your Cobra is a
recent model, the PLL might be completely different than the old PLL02
chips, but the theory should still be the same. There's also a doc on
CB to 6M conversion at
http://6mt.com/index.php?option=com_... 21&Itemid=53.
First thing I could recommend would be to see if you can find a
schematic for your radio. That would allow you to do the math on the
crystals and how they mix to make it work.

Dave gave some good advice here. I do not know if it is true of
modern CB radios, but in the late 1970's, manufacturers started using
bandpass crystal filters in the transmit chain instead of a set of 3
or 4 tuned circuits to clean up the mixing products. This filter had
a secondary purpose too - it prevented the radio from tuning very far
from the original CB channels.

73, Barry WA4VZQ