The AM Forum
March 29, 2024, 11:06:08 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Sonar Marine Radio  (Read 4122 times)
0 Members and 1 Guest are viewing this topic.
W2JBL
Member

Offline Offline

Posts: 676


« on: November 05, 2019, 06:53:12 PM »

   I hvae a Sonar 75AW on the bench right now that I'm converting for mobile use on 160/75/40 and need a schematic or service manual for it. I cut my teeth on these in the marine radio biz back in the mid 70's but a little more info would really help. Nice radio: a pair of 12DQ6 sweep tubes modulated by big germaniaum transistors. I'm up to about 70 watts out and have not even re built the PA tank circuit to match 50 ohms yet, which is a very good sign. The solid state receiver motorboats and needs electrolytics though. A Sonar 75A schematic will also work, the W stands for weather. It's got a converter for VHF weather on board to feeding the built in AM BC tuner. Contact me at radioguy28@aol.com

73
Chris
Logged
WU2D
Contributing
Member
*
Offline Offline

Posts: 1800


CW is just a narrower version of AM


« Reply #1 on: November 17, 2019, 08:43:56 AM »

My Friend Spencer KW2S's Dad designed some of the circuits in those when he worked for Sonar in the 50-60's. Amazing combination of low cost COTS (Commercial off the shelf) parts, with no silly rules - Use what works and keep it cheap!

Mike WU2D
Logged

These are the good old days of AM
W2JBL
Member

Offline Offline

Posts: 676


« Reply #2 on: November 18, 2019, 08:18:40 PM »

After replacing most/all of the electrolytics I now have a great receiver and 100% modulation. I converted the PA to a PI network and bulldozed all the long RF lead lengths, and removed the loading coil. Just plate tune and load controls now, neatly tucked behind the removable speaker panel as before but with real 1/4" shaft knobs. The transmitter puts out 70-80 watts carrier. The rig works great in the mobile but the crystal controled receiver is a limiting factor. So- this will become a transmitter. As I did withthe ARC-5 mobile setup I'm going to build control circuitry with an antenna change over relay and receiver muting. I installed the Alinco DX-SR8 ricebox in the '06 Crown Vic to be used as a receiver today. It's a decent receiver for AM and gives me AM/SSB capabilty on all bands if 75 is quiet.


* NEW TANK CIRCUIT 1.jpg (2780.16 KB, 3264x2448 - viewed 340 times.)

* NEW TANK CIRCUIT 2.jpg (3029.25 KB, 3264x2448 - viewed 298 times.)

* NEW PLATE AND LOAD CONTROLS.jpg (2750.74 KB, 3264x2448 - viewed 339 times.)
Logged
Steve - K4HX
Administrator
Member

Offline Offline

Posts: 2722



« Reply #3 on: November 18, 2019, 10:04:42 PM »

Pretty cool radio. Thanks for sharing.
Logged
KA3EKH
Member

Offline Offline

Posts: 773



WWW
« Reply #4 on: November 19, 2019, 09:51:20 AM »

I have one of these that is the high power version that I picked up at an auction some time back that I would be willing to sell cheap! It has a full set of Marine crystals for receive and transmit and just the stock AM receiver, no VHF converter. Also have the mounting bracket with it.
If anyone is interested I can put up some pictures. It would make a fun 160 meter mobile. Imagine they would work on 160 with no modification but don’t know if they would go to 80. No book or anything like that.
Logged
N1BCG
Member

Offline Offline

Posts: 836


« Reply #5 on: November 19, 2019, 11:46:18 AM »

A VFO or DDS-VFO would make that receiver work great without needing crystals
Logged
W2JBL
Member

Offline Offline

Posts: 676


« Reply #6 on: November 24, 2019, 08:35:32 PM »

    I thought about doing VFO for the receiver using a modified Collins PTO. My father used to put FETs in place of the tube and use them in his QRP projects. But reality set in and realized that I'd have a tunable reciver, but no BFO, product detector or decent AGC for sideband. When there's nobody around on AM and I'm on a long drive I like to tune the bands on a ricebox, so that's why I'm going with a ricebox for the receiver, as I did with the ARC-5 mobile. I have a lot of 80 meter crystals and can easily grind them to every 5 kC in the AM window so crystal controlled TX is not an issue.

      A DDS VFO for the receiver would be very easy to interface. Anyone contemplating a DDS VFO for the transmitter in one of these rigs faces a complete bulldozing of the transmitter. Every AM marine radio I ever worked on used an oscillator with no tuned output. Either a Pierce, or Collpits with just an RF choke in the plate lead. This was to avoid neutraliaztion in the PA and keep the cost down.

  I just had a few more afternoons of fun on this rig doing up the transmit audio. Fun? The whole thing is isolated from chassis ground and is 100% PNP technology and "positive ground". There's a positive and negative rail both above ground, the positive side bypassed to ground. It got even worse when I tried to use my favorite mics: The PTT line goes positive. The audio low lead can not be conected to the chassis, it has to go to the +12 rail and the sleeve of the stereo phone plug for the mic is sitting at +12 volts. 
In the end I replaced the carbon mic with a CB power mic, changed the PTT to ground to transmit and now have to add a relay to control muting the ricebox receiver, and antenna change over relay. I have converted a lot of marine rigs for 75 over the years and most are a one afternoon job. This thing is a full time job in itself. It's worth it though because I get good stable power out and a lot of it. Any time you can get 6 to 8 DB plate modulated watts more than a ricebox in a mobile setup you are going to be a winner. 

   I'd love to find a 100 watt class marine rig by Bendix, Raytheon, or Konel/Narco (as in Narco Avionics). Those rigs used typically 6146's in the PA, and have better NPN based receivers. Konel even used Collins filters in some of their receivers. 
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.07 seconds with 18 queries.