Red Wave Radio

I'm on an email-only account and cannot read this NG so *please*
eamil me any comments you might have regarding the following:

Hi Folks. I've converted a RS TRC-415 cb to 10m (changed the 10.240 MHz
xtal to a 10.635 so that now ch1 = 28.01 MHz, ch2 = 28.02, ...).

My intention was to use this for CW, and I found a spot to splice
the key into (between the xtal oscillator and the driver stages)
that gives pretty clean keying.

Now, how to add a BFO? If its rcvr had the traditional 455 kc IF,
a BFO would be easy to install. But without a schematic I have
no idea what this sythesized rig uses for an IF. Any ideas?

I'm on an email-only account and cannot read this NG so *please*
email me your comments.

Thanks in advance, and 73,
Jeff KH2PZ / 7

Quote:

>Hi Folks. I've converted a RS TRC-415 cb to 10m (changed the 10.240 MHz
>xtal to a 10.635 so that now ch1 = 28.01 MHz, ch2 = 28.02, ...).
>My intention was to use this for CW, and I found a spot to splice
>the key into (between the xtal oscillator and the driver stages)
>that gives pretty clean keying.
>Now, how to add a BFO? If its rcvr had the traditional 455 kc IF,
>a BFO would be easy to install. But without a schematic I have
>no idea what this sythesized rig uses for an IF. Any ideas?

73,
    Dean K5DH

73,

Peter  VK1PK

--
__________________________________________________________
Peter Parker                          

Phone: (06) 285 1004 (ah)
Amateur Radio: VK1PK

Home Page: http://www.pcug.org.au/~parkerp/  
The home of Novice Notes Online and the VK QRP Web Page.
___________________________________________________________

Are you sure the thing is actually working with the new crystal?

I don't know that particular set, but I've seen schematics for
CB sets and the 10.240 crystal is used in a number of places.

Divided down, it is the reference frequency for the sythesizer.  Thus,
if it's changed, the channel spacing changes.  10.240/1024 = 10 KHz.
10.635/1024= 10.385 KHz.

It may be used as a local oscillator (either directly or divided by
2 I think) to mix the output of the VCO down to a lower frequency
before the signal enters the divide by N chain.

If it's a dual conversion receiver, it's used as the second local
oscillator to move from about 10.7MHz down to a 455 KHz second IF.

I thought these were fairly standard, though there were exceptions.
There were also variations, if I recall correctly.  More recent
CB sets used PLL IC"s that did not allow for easy modification.

Depending on the circuit, changing the 10.240 MHz crystal will
not only change the channel spacing, but also, mess with the IF
chain.  The combinations of the oscillators will not line up
the right way, and also if ceramic filters are used in the
receiver, the desired signals will be out of the passband.

As I said, I don't know this rig so perhaps the 10.240 MHz xtal
is used in a different way, though it does seem odd to see that
specific frequency used if the familiar scheme is not used.

As far as the IF frequencies go, you may be lucky.  Open the rig
up again, and look for ceramic filters.  Look for something that
looks like a ceramic capacitor, except it has 3 leads.  If it's there,
it should be marked with a frequency, and chances are more than likely
that it's 10.7.  If it's a cheaper rig, it may not have that filter, or
it may not even be double-conversion.  If it's a more expensive rig,
or it's an SSB rig, then the first filter is bound to be bigger and
will jump at out you when you look inside.  Hopefully it will have
a frequency marked on it.

It's most likely that there is an IF at 455KHz (or perhaps 450KHz),
whether it be the only IF or the second IF frequency.  While in
years past some CB sets did feature Collins mechanical filters, it's
more likely that the filter at this frequency is ceramic.  All of
those that I've seen are in a plastic square or rectangular package,
colored orange or green.  The number of pins depends on the particular
filter.  Again, if you're lucky it too will be marked with it's frequency.

     Michael  VE2BVW

Quote:> I'm on an email-only account and cannot read this NG so *please*
> eamil me any comments you might have regarding the following:

> Hi Folks. I've converted a RS TRC-415 cb to 10m (changed the 10.240 MHz
> xtal to a 10.635 so that now ch1 = 28.01 MHz, ch2 = 28.02, ...).

> My intention was to use this for CW, and I found a spot to splice
> the key into (between the xtal oscillator and the driver stages)
> that gives pretty clean keying.

> Now, how to add a BFO? If its rcvr had the traditional 455 kc IF,
> a BFO would be easy to install. But without a schematic I have
> no idea what this sythesized rig uses for an IF. Any ideas?

> I'm on an email-only account and cannot read this NG so *please*
> email me your comments.

> Thanks in advance, and 73,
> Jeff KH2PZ / 7