The AM Forum

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...

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

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

Or you can do it that way!  ;D

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

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  ;D

Thanks for the replies...

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

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     

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.

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! ;)

The screen is being modulated too.

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

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

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.

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

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

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

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

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.

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

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

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.

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.

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

International Crystal [click] (http://www.icmfg.com/) should be able to hook you up. ;D

Here's a pretty one:

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? 

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.... :)

Not mine - too pretty for me Ted.

MH Electronics quoted me the best price @ $18 each, if I buy 2 or more crystals, any frequency...
http://www.mhelectronics.com/index.shtml

I just ordered the NorCal FCC2 Mk II DDS board. It will run up to 31 MHz, so I would like to use it to put my Whiteface or Blackface up on 10 Meter AM... I'll have to figure that one out...

That's a good price.  I remember when I asked International Crystal for a quote last year (before I had my VFO), for a 3885 crystal in an FT-243 holder for the Globe Scout I used to have, and I just about had a heart attack.  $52!  I just might contact these guys about getting a 39 Mhz crystal to put the FT-301 on 12m.  Thanks for the link to their website.

73,
Ellen - AF9J

I remember that 73 article, nice job!  There were ZILLIONS of those HyGain CB boards out there. Everyone was selling them from Meshna to Olson and dirt cheap. They must have bought them for pennies. HyGain must have lost a fortune. I guess they bought the story that every family would have a couple of CBs and planned production accordingly. When skip is absent I hear almost ZERO on local CB freqs and I live in a major population center. What happened to all those rigs? Of all the ones I used, the KAAR marine CB was the best built. Like a ROCK! Sonar and Pierce Simpson made a quality product as well. International Crystal made a unique one that I'd love to get if anyone has one for sale. It was a 100 milliwatt xtal controlled CB xcvr (with a tuneable rcvr) designed for FCC part 15 license free DX. The xcvr was remotely mounted at the antenna base and the user had a remote control box. Anyone ever see one of these?

73,
AF6IM

A lot of those Hy-Gain boards were for 23 channel units. When the mandatory FCC ruling came in 1977 that you could no longer sell or manufacture 23 channel units, many manufacturers were stuck with tons of raw inventory and finished goods. The Hy-Gain boards were the base for many of the CB's that were being manufactured at this time. At Lafayette at the 11th hour, we were pitching "buy a CB antenna and get a CB for a penny more" just to move the stuff out of inventory.

Actually those early Cybernet boards were rather service friendly and stable, when they moved into the 02A PLL chip they got to be quite fun to work on, I did alot of those years ago. That 02a chip was fun.

They made a rather sloppy VFO for them, see them here and there at the festers.

      Yes, those Cybernet boards and rigs are easy to convert and ubiquitous, only the audio on them stinks. The main problem with them is the audio transformer in there. I have gotten good results by doing the usual fattening up of the caps and replacing the transformer with a multiple output impedance job with normal audio characteristics . Those audio distribution transformers sometimes have multiple output impedances. You know, the 25 or 70 volt things. Have to use the multiple jobs because the transformer is set up as an autotransformer. Of course, it will be very difficult to mount the thing inside, but there is space on the back panels for mounting outside. Its not too ugly. Don't forget the microphone. The usual dynamic cb mic is horrendously pinched sounding. Don't bother changing the transformer if you are going to use one of them. I like to use the Astatic preamp'd crystal/ceramic handheld/mobile mics . They can be had brand new still (cheaper on Ebay). Just change the input resistor in the preamp to  5 or 10 megs or it won't have any low end.
       
        Or nevermind all that and use an external modulator.......Larry