Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Recent Posts

The AM Forum
November 27, 2021, 12:24:00 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1] 2 ... 10
 on: Today at 05:21:43 AM 
Started by W1TTL - Last post by N5RLR
Try pressing on the knob/face with something nonmetallic (a pencil?) and note if the frequency still changes.  If not, I'd guess hand capacitance is coming into play somehow.

 on: Yesterday at 08:09:14 PM 
Started by W1TTL - Last post by W1TTL
Hi W1NB,

Thanks for the reply.  Unfortunately, it's when I press on the VFO knob that the pitch changes.  It's like playing a theramin!

Tony W1TTL

 on: Yesterday at 08:03:27 PM 
Started by W1TTL - Last post by W1NB
Just a thought but in light of the change when putting pressure on the switch, possibly a poorly contacting wafer switch segment?

 on: Yesterday at 03:19:29 PM 
Started by ka1tdq - Last post by ka1tdq
I texted this to Dennis earlier, so I guess I’ll share here as well. I initially thought this was engineering overkill, but now I’ll chalk it up to artistic license. Check out that geared butterfly capacitor!


 on: Yesterday at 11:48:36 AM 
Started by ka1tdq - Last post by W7TFO
Great progress with the old girl, Jon.

Spin the dials and talk to me! Cheesy


 on: November 25, 2021, 09:09:13 PM 
Started by ka1tdq - Last post by ka1tdq
Dennis, W7TFO gave me a completely original Navy TBW-4 transmitter with the condition that I build a power supply for it and put it on the air. I needed to build a pedestal for the transmitter to sit on and a cabinet for the power supply, modulator and controls. The pictures show what I came up with.

They originally used suppressor grid modulation but I'm going to go with plate modulation via a modified Heising configuration and solid state car amp. It'll also sport a high/low power output switch for varying the B+ on the final. I'll have a spot switch as well and an AM/CW mode switch. Not really necessary but it'll also have a soft start circuit with permissives.

The receiver, as usual, will be an SDR play.


 on: November 25, 2021, 07:54:20 AM 
Started by W1TTL - Last post by W1TTL
Hi everyone,

I'm hoping that someone can help me crack this nut I've been trying to fix for the past couple of weeks.

I have a Johnson Ranger with the early keyer platform.  I've replaced all the electrolytics as well as R3 with a 5W 18K metal resistor.  The usual stuff.

I primarily operate CW.  When I have it on 80m, either when zeroing or transmitting, the CW note is rock solid.  However, when on 40m or 20m, the CW note drifts down in frequency, even after warming up for an hour.  This is whether I am zeroing or transmitting into a dummy load.  

Aha, I thought.  Must be a problem in the 40/20 section of the VFO.  So, I replaced the temperature coefficient capacitors (C10, C11) with "dog bone" capacitors of the appropriate types as well as the mica capacitors (C12, C13).  (I got the N150 and NP0 capacitors from Surplus Sales of Nebraska -- they didn't have the exact values so I had to mix and match values in parallel to add up to the correct values.) I also cleaned the band switch in the VFO with deoxit.

Still no luck.  VFO drifts in 40m and 20m.  Oddly enough, when I push on the VFO knob (or on the face around the VFO knob) with everything back together, that makes the VFO go up in frequency with the pressure.  I made sure all the screws and nuts were tight for holding the VFO box together.  The top of the VFO is grounded to the face of the Ranger with a short connection.  I tried W8JI's recommendations for grounding the plate tuning capacitor to the chassis to fix drift.  That didn't cure my issue, so I put the insulator washers back.

I swapped the 6AU6 with a 6AH6 and that didn't fix the VFO drift.  I also monitored the voltage at pin 1 on the OA2 regulator and it stays around 149VDC, only dropping 0.4V on transmit.  I also replaced all the mica capacitors in the VFO as well as any suspect resistors, even though they're not part of the 40/20 circuit in the VFO.  

Any ideas as to what might be causing my VFO drift woes?  I don't get it -- my Valiant's VFO, which is basically the same VFO, is rock solid.  Thanks for any ideas.

73 and Happy Thanksgiving!

Tony W1TTL

 on: November 24, 2021, 11:19:13 PM 
Started by WA2ONK - Last post by WA2ONK
I live in the Trenton, NJ area. Looking for some 2m am activity. I can run up to 200w and am using a 12 element horizontal yagi. If interested in giving it a try, email is wa2onk at verizon.net

 on: November 24, 2021, 05:41:11 PM 
Started by W1TTL - Last post by W1TTL
Hi everyone,

I'm looking for a Ranger (not the Ranger II) that has the CW keying addition in the Connecticut area.  Please let me know if you have one for sale.  Thanks!

Tony W1TTL

 on: November 24, 2021, 04:33:39 PM 
Started by W9BHI - Last post by vk3alk
Hi Don..

To make a 3 bander is quite simple and easy to do but you just have to know a few things…..
To keep it short for reliability and simplicity the best TX modules to use are H Bridge design….
On 160M and 80M its very easy to make a dual bander as at those frequencies these modules act as switch only and resonances are a long way away…..
40M is a little more difficult due to the lack of squarewaves....
To overcome this you use the gate capacitance of the FETs and add a bit of inductance to assist the driver in developing enough voltage swing...
On my posting of a 40M transmitter you can see things although now the output transformer is different….…
This TX works on 160M 80M and 40M without any extra components added during band switching ….
Have tested the transmitter on all bands to 300 watts only which is the limit of my bench test power supply …… efficiencies are well into the 90% region….
Of cause the choice of FET is critical to all this ....  since this semiconductor business has happened they are not being manufactured for another 18 months…..


Pages: [1] 2 ... 10
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 0.05 seconds with 14 queries.