The AM Forum
March 28, 2024, 10:14:02 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: SP-200/BC-799 make it get BC band??  (Read 6113 times)
0 Members and 1 Guest are viewing this topic.
WBear2GCR
Member

Offline Offline

Posts: 4135


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« on: October 16, 2014, 08:00:58 PM »

Ok kids,

Got me a BC-799A (Howard) thanks to Steve, W2TRH via Nearfeast.

Has (as you know) two completely worthless bands. Below broadcast.
Looking at the downloaded manual, the BC-1004 is the same radio but has the bands.

This is single conversion, and the difference is in the coils of the two lowest bands.
I figure that I could take turns off the coils (go higher in freq) and put the two useless bands onto the BC band. Yes, I know the dial will not say the right thing, and that I may not get it dead bang where it would be stock. But with a sig gen, scope and or/grid dip meter, one ought to be able to get it to where it ought to be.

Better still if someone could measure the L of them.

Any comments?

Any happen to have spare BC-1004 or equivalent main dials?
Or a BC-1004 band switch knobber? Cheesy

                              _-_-

PS. I do have a rust-o-bucket that I could pull coils from...
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
N8ETQ
Member

Offline Offline

Posts: 795


Mort


« Reply #1 on: October 16, 2014, 09:29:15 PM »


   I haven't had time to mess with it but thought it
would be cool to move the 100kc-200kc band to
1 - 2 MC..  And let him get 160m too.

    Anyone with a scrapped out rig with the dial should
also have the coil/cap assemblies from the turret.

GL

/Dan
Logged
WA2IXP
Member

Offline Offline

Posts: 48


« Reply #2 on: October 16, 2014, 10:02:54 PM »

I have a bc-779 also. Wanted to use it on 160 meters but no coverage as you pointed out. Was a nice set and it worked well. I built a converter using a 6sa7. Used a 4.5 mc crystal on the first grid and put the antenna in on the other with a 500uuf variable cap and a coil from an old TRF broadcast radio. The plate of the 6sa7 has an rf choke feeding it and the output goes in to the reciever thru a small coupling cap. Tune the BC-779 on the 40 meter band.  Works fine. Power comes from set. I used a wafer switch to switch the ant and also turn the heater of the 6sa7 on and off. Also hooked up the AVC but I found it not really needed. All this is on a 2 inch rack panel above the reciever in a rack. I also have a similar set , a SP-200 I believe, Which does have better band coverage. In going over it I found that someone had added some temperature compensating caps on the osc and rf sections. Makes a world of difference compared to the other set as far as the first 2 or so hours of warm up required for it to settle down. The surplus Conversion Handbook  has a simple triode mixer/osc circuit with out the tuned input that should work ok for B.C.stations too.
                              jay-
Logged
WBear2GCR
Member

Offline Offline

Posts: 4135


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #3 on: October 17, 2014, 10:37:07 AM »

Curious about the "temperature compensating caps"?

What sort of caps were used?

Presuming something small placed across or in shunt with otherwise "stable" caps?
Like a Z5U type??

One of the bama schematics shows where someone put a gas vreg tube inline with the HF-OSC.

Still learning about this radios innards. Would like to do whatever I do inside the radio, and not by using a converter that is external. But the external converter is a neat idea too.

                      _-_-
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
WBear2GCR
Member

Offline Offline

Posts: 4135


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #4 on: October 17, 2014, 10:58:38 AM »


Probably this:

http://amfone.net/Amforum/index.php?topic=15703.0;wap2
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
W7TFO
WTF-OVER in 7 land Dennis
Contributing
Member
*
Offline Offline

Posts: 2521


IN A TRIODE NO ONE CAN HEAR YOUR SCREEN


WWW
« Reply #5 on: October 18, 2014, 12:14:39 PM »

I've used a 4pFN750 cap in the osc stage of my SP-10 & SP-100's.  It does help noticeably with warm-up drift.

73DG
Logged

Just pacing the Farady cage...
WA2IXP
Member

Offline Offline

Posts: 48


« Reply #6 on: October 19, 2014, 10:06:16 PM »

Yes,
  That's the article. Were several CQ articles covering these sets. I poked around and changed a few caps at first but then took out the coil box and changed all of them. With the coil box out and the panel off the rest of the circuitry is alot easier to get to. Was amazed at how well it worked. Included a pix of the 160/BC converter.


* 003.JPG (472.77 KB, 2272x1704 - viewed 570 times.)
Logged
WBear2GCR
Member

Offline Offline

Posts: 4135


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #7 on: October 20, 2014, 07:38:23 PM »

So what are we looking at?

Did you wind ur own Ant coil there?
Add a front panel slug tune screw?

            _-_-
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
WA2IXP
Member

Offline Offline

Posts: 48


« Reply #8 on: October 21, 2014, 09:00:39 PM »

The antenna coil came from an old trf broadcast radio. Had a link winding as well as the grid winding. The slug was added to get to the bottom of the b.c. band screwed in some and up to 2mc screwed out. At first I was only thinking of 160. Then added the slug later.
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 0.054 seconds with 18 queries.