Wilderness / Norcal 40a question
I just recieved my kit and want to do the frequency coverage expansion mod. I understand that it only takes changing one capacitor (a 47pf is supplied) to one of greater value and you can get up to 150 KHZ of coverage. Anyone know what value cap I should put in there? I don't see it in the book or online anywhere.
Even if you did the mod and didn't go for a full 150 KHZ, would you kindly let me know what you used and what kind of coverage it got you?
Have you contacted Bob Dyer at Wilderness Radio?
P.O. Box 3422
Joplin, MO 64803-3422
"The Electronics of Radio" written by David Rutledge, an amateur and professor at Cal Tech, is a textbook for his EE20 class which uses the Norcal 40A in all the lab exercises.
Cal Tech was also selling the EE20 class notes at one time.
Norcal 40a mods
eHam.net Reviews from owners
Last edited by W9GB; 02-26-2009 at 03:03 PM.
Like a dope, I thought of that right after I posted here. I did email him, but since he doesn't mention values in the book, perhaps he wants you to figure it out for yourself (encourage "experimenting?"). I'm still kinda surprised that I've been unable to find the answer in either the book, wilderness web site, or 15 googled pages.
Still, if anyone wants to help a brother out....
Got an answer back from Bob. (I post it here so anyone else might have an easier time in the future).
If you double c49, you will nearly double the range, so adding 47 to 100 pf in parallel should do it. Be sure to use
high quality caps, either npo or silver mica types to insure vfo stability.
Norcal 40a builder N1KSN commented, in eHam.net, that he had to add a turn (from 60 to 61 turns) on the VFO torroid core for better alignment & frequency coverage in the CW Extra portion of 40 meters (7.000 to 7.025 MHz).
Last edited by W9GB; 02-28-2009 at 03:21 PM.
Interesting... The instructions mention that if you plan on using the novice band, then to wind one of the toroids to 58 turns instead of 60. Must be talking about the same toroid??? But I'm in the novice band for now...
There is no novice band on 40m anymore. You can run CW from 7025 to 7125.
Originally Posted by KB8NHL
I built my 40A in 1998, and what I do is just adjust the air variable cap that is near the front of the rig. I have about 50 Khz of bandwidth and by adjusting that air variable I can slide that "window" up and down the band. I also installed a 10 turn pot to make the tuning a bit smoother. If you do the 150 Khz tuning mod, make sure you replace the tuning pot with a 10 turn device or you will fly by stations so fast you won't even hear them.
It's a great rig, I still use mine once or twice a month. It was the first rig I ever built.
The Novice band allocation on 40 meters has changed a few times, since I was first a Novice
The instructions mention that if you plan on using the novice band, then to wind one of the toroids to 58 turns instead of 60. Must be talking about the same toroid??? But I'm in the novice band for now...
In the 1970s, the 40 meter Novice band was 7.15 to 7.20 MHz ...
which made the 100 kHz SSB/AM segment crowded on some evenings with the foreign broadcasters!
The Novice segment was then moved (WARC 79 timeframe?) to 7.10 to 7.15 MHz, expanding the SSB/AM portion another 50 kHz.
IF I was building a Norcal 40a today, I would set up the VFO for 100 kHz
7.0 to 7.1 MHz ... or ... 7.025 to 7.125 MHz.
AE5X has the Multi-turn pot mod with part numbers
Last edited by W9GB; 02-28-2009 at 03:55 PM.
Now I'm wondering how many turns I should use. I definately want to cover from 7025 to 7125. I figured by setting up to cover from 7000 to 7150, I'd not be hurt if performance was unstable or something at the fringes. (Maybe I'm barking up the wrong tree, ubt that was my thinking). So, the instructions read as below: to make that toroid 58 turns instead of 60 for operation on "the novice band." I wanted to wind those toroids as soon as I get home from work in a few hours...I wonder if bob answers emails on saturdays...
Oh, I did order a ten turn version of the pots listed by ae5x a couple days ago...It'd be nice if it was waiting for me when get home, but UPS doesn't do saturdays, do they?
Last edited by KB8NHL; 02-28-2009 at 06:26 PM.
For the archive:
and the super-speedy response (On a Saturday, no less!):
> Thanks Bob, and I'm sorry to be a pest but I think this should be it:
> Regarding winding the toroid to 58 turns instead of 60 for operating on
> the "novice band." I'm wondering if that is current info, or off of the
> older band allocation data? Bottom line, I'm add capacitance at C49 for
> 150KHZ of coverage. I hope to cover from 7000 to 7150. Would that be a
> 58 turn toroid?
If you are going to make the range 150 khz, wind it with 60 turns. You will
also have a 35 khz swing with the air variable
trimmer when you set the band edge. Each turn is about 35 khz as well.
The kit is awesome to build, it looks so neat and uncluttered.
The support is above and beyond, I hope that Bob is able to retire a wealthy man from his kits.