Getting Back to the Homebrew Subject

[ka3zlr]

Well, I don't think I will tackle a ribbon mic. I made a dynamic once that was ok, but Bob Heil convinced me his were superior in everyway.

Unfinished transmitter at right top shelf is a dual 807 modulated by 807's wired as triodes. I used 807's because I have several of them all unused in original military boxes. It has a self contained PS, exciter and audio driver. It is 160/80/40 plug in coils. I modified old Wilcox 99A coils for it. It will be xtal controlled or I can use my hb vfo when I find a cabinet for it. I took the cabinet for the small receiver. My antenna is an aborted off center zepp with the short leg grounded and about 21 feet high. The open line comes into shack were it matches 52 ohm coax almost perfect at 3860 and covers 3840 to 3900 with little swr.

Well, hope to see photos of your homebrew projects and hear them on the air.

I learned homebrewing from my dad, an avid homebrewer and kit builder. Most valuable were Bill Orr handbooks and close ham friends who are homebrewers and retired broadcast engineers. Thanks for your comments and opinions even if they differ from mine. We all have varied interest and mine is vintage style homebrewing ham gear and building triode audio amps for guitars, etc.

Thanks for the photos of the 813 amp and ribbon mic, very nicely done. What will you use to modulate the 813 amp? 811A's are nice, but I prefer triode wired 813's at zero bias. 73 sAM

 I'll tell ya Sam i'm not sure which way i'm gona go this time, I left HF some years ago sold alot of stuff off and moved up in frequency into Microwave and uhf and was doing some things there with a gud friend of mine and his name is jack too I did put together a Motorola DSP system last year for 160 SSB, and worked the guys on the 1721 group that moved down there i picked those chips up on ebay and the tech i bought them off of gave me the coding for them it was a closed binary system but it worked off an old HP lap top in DOS and had a ball last season with them guys on 1872.

 So i am just coming back in here, been off the board for awhile, and one day just got the urge and signed back up, so you and i are the newbies i guess... but Hey you rocked the system here...You have a beauty of a station there...Fine Buisness Old Man...

over to you om...

[k4kyv]

The big transmitter is a 813 class C RF at 300 watts out. It is modulated by a pair of 813's wired as triodes (Bill Orr handbooks have info) producing 500 watts peak in class B. I usually hold peaks to 450 watts. The RF deck uses a swinging link isolated from plate dc by a 500 mmfd doorknob. I use a 6kv National cap for tuning.

Mine uses a pair of HF-300 triodes in pushpull, modulated by a pair of 810's in class-B.  My first high power modulator in the late 60's used triode connected 813's.

I use a dual 240 pf 7000 volt plate tuning cap, that I re-assembled with parts from three EF Johnson air variables.  I don't isolate my tank coil from DC.  The tank coil and split stator capacitor are all at full modulated HV DC potential, mounted on standoff insulators, with an insulated shaft coupling to the control dial. 

Series fed DC eliminates the big RF plate chokes, which are always prone to give trouble.  The plates of the tubes are series fed through the tank coil.  The only  rf choke is a small beehive 2.5 mHy choke rated at about 600 MA, used to feed the HV to the the midtap of the tank coil where the rf potential is at a minimum.  Even though the full modulated HV appears between the main tank coil and the swinging link, in the 35 years since I first built the transmitter I have never seen it arc over.  If it did, it would simply cause the overload relay to kick out before any damage was done.  However, I wouldn't recommend placing one hand on the transmitter cabinet while touching the ungrounded rf output line to the antenna tuner while the HV is on.  That's a moot point right now, because that line from the link is grounded on one side using the present coupling system.

http://amfone.net/Gallery2/v/stations/k4kyv/IMAG0016.JPG.html

[N3DRB The Derb]

my swingin link HB rig also used full b+ through the output coil. never a problem. Notice complete and utter lack of safety shield, etc.etc. 

[W7XXX]

awesome rigs guys and nice engineering. I used the 3x 813 with the dc fed thru a Wilcox 99A choke (same as Art 13) to center tap coil for several years with 125% positive modulation, but when I got the Heil mic I increased the positive modulation over 125% and experienced occasional arcing as the ac component is increased, so I went with the dc blocking cap and changed out the old Hammurlund caps with unused Nationals. I tune with a dual 50mmfd and have an identical cap mounted on top as a trimmer. Makes tuning smoother and I can keep resonance about half capacitance.

The original set up used doorknobs instead of insulators for mounting the tuning cap and thus a short RF path to gnd and neat look. I thought I was original and then I saw this used in the Bill Orr Handbook. With the current set up the cap is grounded. I will try and find the photos of the inside before and after I have on CD somwhere. I built this rig in 1999.

Hey Don do you remember the SPAM group before AMI? I am looking forward to working you sometime ... I hate to mention this but you look at lot like me ... lol ...

Slopbuckets ?... lol ... you must have known Ricardo.

Here is something I wrote in the early 90's.

ODE to AM

In days of old
When hams were bold
and sideband wasn't invented

We tuned our load to the center of the mode
and talked away very contented!

[k4kyv]

Hey Don do you remember the SPAM group before AMI?

I knew Hoisy, W4CJL (SK), the founder of the original SPAM, personally.  He later turned it over to Floyd Dunlap WA5TWF who unexpectedly went SK a few years later. A dude in CA (can't remember his name/callsign off the top of my head) took over from Floyd.  He was a real  flash in a pan.  He hit the ground running, but shortly thereafter he just vanished off the  face of the earth and took SPAM with him.  As far as I know no-one has ever heard from him since.

Slopbuckets ?... lol ... you must have known Ricardo.

I still have the "I hate slopbuckets" T-shirt that Ricardo sent me.  He is not the originator of the term, though.  It has been around since the 50's.

[W7XXX]

Don, Have you ever experiemented with Taylor modulation?

[W7XXX]

Nice looking rigs Mack! Hey no problem for me to strip a Collins out. Stripped an ART-13 once for homebrew parts. If the parts are worth more than the rig, I will strip it before I sell it cheap and buy the parts from someones else for more money. I have stripped Johnson and Heathkit transmitters, National, Hammurland, and Collins receivers and lots of military stuff. The military gear really has some high quality parts.

[W7XXX]

[W8EJO]

Here is an exceptionally beautiful example of a recently completed (by KC9KEP) 1941 ARRL Handbook (pp117-121) superhet/regen receiver. Full details here:

http://antiqueradios.com/forums/viewtopic.php?t=79737

[KB2WIG]

shhaazzzAM!!

[W3RSW]

Absolutely gorgeous.
If I didn't see the logo I'd swear it was a commercial product.  Maybe you ought to go into production.  Today's prices for components (of the obtanium variaty) probably $500.

[k4kyv]

[Ed/KB1HYS]

Don, is that photo of a real rig???   talk about a breadboard!!! 

I'd be afraid I'd find the B+ with some part of the anatomy...

[k4kyv]

Don, is that photo of a real rig???   

Yes.  This "bookshelf transmitter" is the handy-work of Clyde K4UXK of Columbia Tn.  A single 833 modulated by a pair of 833's. One of the better sounding homebrew AM rigs on 75 and 160.

[w8khk]

The original set up used doorknobs instead of insulators for mounting the tuning cap and thus a short RF path to gnd and neat look. I thought I was original and then I saw this used in the Bill Orr Handbook.

My Grandfather's KW rig (W8YNG, father of W2DU) used this technique of mounting the plate capacitor for a pair of push-pull 250-TH's.  He purchased this rig used in 1937, so the method may even pre-date Bill Orr's writings.  I have just finished restoring this final, and hope to have it on 40 meter AM in the near future.  I also restored my dad's (W2DU) push-pull 304TL final and will have that on 75 meter AM.  (This was the rig he had on AM in the 70's, when Bacon suggested he swap the modulator grid caps to get more upward modulation!)  I still have lots of work to do on the power supplies and audio chain, so it will be a while before I have anything more than the 32V2 operational.

[Steve - WB3HUZ]

That is awesome Rick! Can't wait to hear this piece of history on the air again. That's cool you have your father's original call.

The original set up used doorknobs instead of insulators for mounting the tuning cap and thus a short RF path to gnd and neat look. I thought I was original and then I saw this used in the Bill Orr Handbook.

My Grandfather's KW rig (W8YNG, father of W2DU) used this technique of mounting the plate capacitor for a pair of push-pull 250-TH's.  He purchased this rig used in 1937, so the method may even pre-date Bill Orr's writings.  I have just finished restoring this final, and hope to have it on 40 meter AM in the near future.  I also restored my dad's (W2DU) push-pull 304TL final and will have that on 75 meter AM.  (This was the rig he had on AM in the 70's, when Bacon suggested he swap the modulator grid caps to get more upward modulation!)  I still have lots of work to do on the power supplies and audio chain, so it will be a while before I have anything more than the 32V2 operational.

[WA1GFZ]

Now that is cool your GF's rig. I wonder if he ever ran spark?.....I have my GF's fig tree, pick ax.......and his desk light.....

[w8khk]

Steve, when I upgraded to Extra, I debated whether to apply for my grandfather's or dad's call.  I decided on W8KHK, and I tried to keep it quiet.  I was to meet dad at the Dayton Hamvention, and the plan was to get a hat with my new call, and see how long it took him to notice.  But he was perusing the web and discovered I had the call a week before Dayton!

I posted a couple pics, the first one shows the W8YNG rig on the left, with the aluminum panels.  To the right is the black wrinkle p-p 304TL rig dad built in our Cranbury NJ apartment when I was between 1 and 2 years old.  

The second photo is a back view of the restored 304TL final, taken in my back yard in Marietta, Ga.   Hope to have it on the air soon!

[w8khk]

Now that is cool your GF's rig. I wonder if he ever ran spark?.....I have my GF's fig tree, pick ax.......and his desk light.....

No, Frank, he was not on spark, to the best of my knowledge.  Although my gradfather taught my dad how to build a one-tube regen receiver, dad actually got his ham ticket first, in '34. grandfather got his a few years later.  I do remember my grandfather gave me a Wen soldering gun when I was 5, and I built a three tube amplifier (5Y3, 6J5, 6K6) when I was 6. Been homebrewing ever since.  After I get the 75 and 40 rigs on AM, I will then work on getting the RCA BTA1-MX I purchased from Tim (WD4TC) up on 160.  So many projects, so little time!!!!