Playing with a 60's vintage Courier 23 for conversion to 10 meters

[W5EFR]

Well, I recently acquired a ECI Courier 23 11 meter radio.

I'm thinking I'm 2 crystals away from putting it on the 10 meter AM band (it will pretty much cover the entire 10 meter AM band), a lot cheaper than buying 2 crystals per frequency if I put my Johnson Messenger II up there.

I was looking at the schematic for it and I believe it is Heising Plate modulated...is this correct, or is it just screen modulation?

http://riley-music.com/BowsStuff/Courier23/Courier23PlusSch.pdf

The audio chain caps are going to get changed for 0.22uf (from the stock 0.005uf caps) to give me some more audio range, although it doesn't sound too bad now.

I figure that if I can change the TX mixer crystal to a 4.000 MHz and change the RX mixer crystal to a 3.545 MHz, or change the TX mixer crystal to a 4.005 MHz, and change the RX mixer crystal to a 3.550 MHz, it will put me well into the 10 meter AM band...

[WD8BIL]

To reach 29.000Mhz (where the AM activity is) with the bandswitch at ch.21. the transmit mixer freq is;

37.85(xtal 2) - 4.635(xtal 1) - 29.000 = 4.215mhz

That'll give you 4 channels in that region;

ch 21 = 29.00, ch 22 = 29.01, ch 22A = 29.02, ch 23 = 29.04

Since the transmit mixer is now 4.215 then the recieve mix should be;

4.215 - .455 = 3.760mhz.

FYI: ch1 becomes; 37.60 - 4.635 - 4.215 = 28.75mhz

[W5EFR]

Roger that...

I had figured:

TX      RX        High      Low         Freq      Channel
4.005   3.550   37.600   4.635      28.960      1
4.005   3.550   37.600   4.625      28.970      2
4.005   3.550   37.600   4.615      28.980      3
4.005   3.550   37.600   4.595      29.000      4
4.005   3.550   37.650   4.635      29.010      5
4.005   3.550   37.650   4.625      29.020      6
4.005   3.550   37.650   4.615      29.030      7
4.005   3.550   37.650   4.595      29.050      8
4.005   3.550   37.700   4.635      29.060      9
4.005   3.550   37.700   4.625      29.070      10
4.005   3.550   37.700   4.615      29.080      11
4.005   3.550   37.700   4.595      29.100      12
4.005   3.550   37.750   4.635      29.110      13
4.005   3.550   37.750   4.625      29.120      14
4.005   3.550   37.750   4.615      29.130      15
4.005   3.550   37.750   4.595      29.150      16
4.005   3.550   37.800   4.635      29.160      17
4.005   3.550   37.800   4.625      29.170      18
4.005   3.550   37.800   4.615      29.180      19
4.005   3.550   37.800   4.595      29.200      20
4.005   3.550   37.850   4.635      29.210      21
4.005   3.550   37.850   4.625      29.220      22
4.005   3.550   37.850   4.615      29.230      22A
4.005   3.550   37.850   4.595      29.250      23

[WD8BIL]

Or you can do it that way! 

I've done 8 11 to 10 meter conversions on different rigs and had no problem with alignments in any of them. Good luck.

[W5EFR]

I was just looking for the easiest way.. I was looking at changing the 37 MHz crystals to 39 MHz.. and then I thought.. Wait a minute.. I could change 2 crystals and save a lot of cash 

Thanks for the replies...

So what do you think about the modulation? Is it screen, Heising, of a combo of Screen/plate?

[w4bfs]

Hi Bow ... looks like split impedance (autotransformer) Heising to me ... the modulator tube operates at at lower impedance than the plate modulated rf stage ... before my pop got his ham ticket, he op'ed one of these ... audio quality clear and crispy with a d104 mic (unamplifiied) ...hope this helps...73...John     

[Steve - WB3HUZ]

It's Heising modulation and a rather common version of it when using an audio output tranny, where the modulator tube is tapped down on the choke while the DC passes through the entire choke. The secondary is only engaged on receive to drive the speaker.

[W5EFR]

Thanks Gents!

I thought it was screen at first, then I compared it to some of teh heising circuits in the William Orr Radio Handbook and started to change my mind.

Thanks for the clarification.. I'm learning this stuff as fast as I have projects to challenge me!

[Steve - WB3HUZ]

The screen is being modulated too.

[N3DRB The Derb]

dont forget to put a power mike on it or no one will hear you......

[Ed-VA3ES]

You could always  short out R19, the 330 ohm, 1W resistor and R 79, the 100 ohm, 5 W job, for more output!   

And don't forget the "10Kc switch" to put it on the RC channels!!!!   Actually useful for 10M.   All you need is  a DPDT switch in the crystal circuit to enable the missing channels.

[w4bfs]

so Ed ... Is that where a big STRAPPING signal came from? ... beefus

[W5EFR]

You know, you guys sure know a lot of "tricks of the trade" in the cb world... I'm sure none of you ever operated there.... 

CB'er comments aside...

I have thought about putting my FCC1/FCC2 DDS circuit to work to put this thing on 10 Meters.

Since the FCC2 has dual VFO ability, as well as an IF Offset ability, I would just need to tie into the keying relay and use a relay to key the FCC2 for the IF shift. Then I could pull out the 6 MHz TX crystal and the 5.545 MHz RX crystal and tie the DDS into there... I believe

[Ed-VA3ES]

so Ed ... Is that where a big STRAPPING signal came from? ... beefus

I know nothing! Nothing!    (It's  a great big 3dB gain... if that!)   

[w4bfs]

Brian .. I still have a couple of FS23 ...do you have 10 meter mod info? ... thanks ... John

[K3ZS]

Sometime in the 70's or 80's I was involved in converting CB circuit boards to making 10M FM transceivers.   I wrote a conversion article for 73 Magazine, which I never got credit for, I suppose because they paid me for it.    Anyway, these boards were for many transceivers, they were mostly called Hygain boards.    They used a synthesizer IC and required only changing one crystal for conversion to 10M and retuning.    I am planning on unconverting the one I made for 10 FM back to AM and moving down to 29.0 MHz range.    I had built a 50W single transistor amplifier for it.    I think with some bias I can make it linear and use it for AM also.   It is a much cheaper way to get a CB conversion than the crystalplex schemes of the older CB rigs.

[kb3ouk]

wish i had a cb to convert to 10 meters. how easy is it to do?
Shelby KB3OUK

[kb3ouk]

those would be pretty good rigs if they ran 40 watts.
shelby kb3ouk

[Pete, WA2CWA]

those would be pretty good rigs if they ran 40 watts.
shelby kb3ouk

I can't remember all of the details, but 11 meters was one of our ham bands. It then became a commercial band, I think, for a very shot time until the FCC finally made it the public citizens band. Those blue face commercial Courier's came from an old deliver truck and base setup before the CB band was established. They were really old. Much older than the Courier CB stuff from the 1960's. I did some search’s, but I cant find or remember the model numbers.

I pulled this down off some web site some time ago:
The 11 meter band was never a primary amateur band. 1947 -The Atlantic City Conference - Amateurs lose parts of 10 meters and 20 meters, but will gain a new band at 15 meters in 1952. To compensate for the loss, the FCC allows use of the 11 meter band (26.96 to 27.23 Mc) on a shared basis with Industrial, Scientific and Medical devices.

Early 1957
FCC Docket #11994 proposes reallocating Class D in the very underused 11 meters Ham band 26.96-27.23 MHz (USA-only). At this time there was little business/military use of 27MHz and model control on 27.255 was inadequate, being shared with paging and other services.

11th Sept 1958
The 11 meters ham band is reassigned to models and Class D Citizens' Band radio.

Maybe the Courier you're thinking of is the Fleet Courier.

[ka3zlr]

I always enjoy reading what comes up for 10 meter on here, now that we're on the upswing it's great to monitor the sig-in-nails on 10 coming in.

I like the Black face too, tunable receive is nice, put an analog meter in mine, Rocks are the problem there, anyone have a link on who's cutting rocks for them could use a few more here on my end.

73 jack.

[Opcom]

dont forget to put a power mike on it or no one will hear you......

Power Mic...

Your are right though, a Courier 23 will require an amplified D104 to overcome the capacitance between the grid and the plate on the mic amp tube. Its not like a Johnson or other amateur rig.

I'll tell you what’s way better than Courier 23 is a Sonar FS-23. It has a much better receiver for use on 10 meters.

OOOHHH.. I has two of them also! These things are the Best 23-channel CB for AM!  -and run on 12V as well.

[N5RLR]

...Rocks are the problem there, anyone have a link on who's cutting rocks for them could use a few more here on my end.

International Crystal [click] should be able to hook you up.

[Pete, WA2CWA]

Here's a pretty one:

[Todd, KA1KAQ]

They sure knew how to make sets attractive back then. Blue hammertone, polished aluminum knobs, chromed cabinet... nice stuff. I've got one like this, also one of the older black-faced Fleet Couriers along with a 'new' pair that came out of the West Topsham fire engines back in the early 80s. IIRC, the last model uses a big Compactron output tube that provides considerably higher power out. They were considered business band sets and not regulated the same as 11m stuff.

The Model 23 was made in two versions (dressed up differently over the years), one of which had the 'Range Boost' switch under the meter for increasing the modulation. They're pretty straightforward rigs to work on and should produce 8-10 watts out when adjusted properly. A number of companies including Radio Shack sold re-badged versions, so there are plenty of them around.

The old Johnson Messenger I is another favorite with the 10m folks. Power not being an issue when the band is open, frequency agility is the only limiting factor. But isn't that part of the fun? 

[ka3zlr]

Boy that one Pete got is in Super shape..wholly cats I haven't seen one of them in years....

Thanks for the Link Mike....