The AM Forum

I am posting this in the Technical section as it will undoubtedly get technical!

I have created a page to document the progress of the 813 X 813 rig.


http://tinyurl.com/4dmckxp

Rich

All the pics don't load on your web page.  Only the first one.  Changed to "Safari" and it works fine. Thanks

website works fine on firefox and osx 10.6.5.

Very nice work ! I would be interested in hearing how the exciter
behaves (and some details on voltages, etc.).

Peter

Peter,
    I am using the lower voltage (about 2200 unloaded) on the HV transformer, at least initially.  The 90800 is getting about 400V and, as I recall, was putting out 10-15 Watts.

Rich

 

that's neat. Did you have any problems when the osc and PA are at the
sane freq ?

I am not following...

I think he's talking about straight through -- no multiplication.
I saw the previous thread on your home brew chassis. Really nice! Have you ever tried the hand grinder fitted with a cutoff blade?
Going to check out your newest pics right now.
 
73, Phil

Dead pics.

C

They're up, Clark. I just looked at them.

Super neat construction!

Nice Job Rich......Those 813's look new

Red xs on laptop, Computer and phone.  Oh well.

C

Well Dang!   I tried to keep it simple.  I made it using word and uploaded the htm file and the directory containing the associated files to my web host. 

Web experts out there?

Rich

PS  I re-uploaded them in case that helps.....

It took about 60 seconds, but they all loaded fine for me using xplorer 8.
Very nice work, I hope mine looks that good some future day.

Hmm.. I got them up now..  I had to refresh it a bunch of times and they came up. I wonder if they are very large MB Pics?


Anyways.. Looks good!

C

I replaced the images with re-sized ones, I hope I did not break it....


Rich

Rich,
Wonder if you will be making it to winterfest this year.  It will be Saturday Jan 29 this year in Mineral.  I have some jewels that are part of the pac nw national trust.
ka7woc

I have run that date by the powers-that-be and it is looking good!  The NW trust?  Like my K7LFE linear that I was instructed, by the person I bought it from, to sell for what I paid?  ;-)

Rich

Works with SeaMonkey.  Nice work!

looks good

Kudos! :D

73DG

Hi Rich,

Yes, nice layout and packaging. I think she'll be a beauty when she's all done.

We all look forward to seeing the rig when it is completed.

73,

Bruce

(http://likesirl.com/images/logo.png)

I see lots of Teflon wire in there - good going!

This rig is turning out to be one of the best 813's rigs I've seen to date. Very heavy duty metalwork and laid out with good planning.

As they say, if it's worth building, it's worth building right.


BTW, when you get there, don't let the neutralization adjustments throw you.  With all voltages off, put some 7.0 mhz RF into the grid circuit (50 ohms) and attach the scope probe to the tank circuit. Key the amp. Add or subtract sampler plate area (if needed) and move the sampler plate back and forth from the tube until you get a nice range of adjustment with the neut tuning cap as you watch the RF signal on the scope. Then just dip the signal to minimum using the neut  adj cap and you're all set.

Do it on 40M and shud be OK on the other bands. The 813 tetrode is usually very stable in RF service and many guys don't even bother to neutralize them. So the adjustment does not have to be perfect on all bands. But it will be more stable than without neut in the end.

T

Loads fast and looks fine on IE9.

Its looking good.

Loads fine here also. I like the compactness of the PS, I also hate wasting space.


Just a side comment for others....the 1N5408 diode is only rated at its full 3A with at least 1/2" of lead exposed, with the way some sharply bend the leads right after the body and mount in a PC board seriously derates them. Rich has plenty of lead exposed, especially for that QRP amp ;D

Carl

Did you ever see the one John KC2FXE built? It looks great ;D ;D ;D

A few places I worked actually used thick brass posts with a hole down the middle for the lead. This would help pull heat away from the diode. The posts would be pressed into a PC board.  

That rig is bahyewtifull!!  Quite the behemoth.

Rich

And it a  JJ rig. Where did you find it?

Very nice Rich!

Much envy here. No time now to work on mine, have to go back to the “Pen”
for 16 more weeks. >:(
I like how You protected the PS switches with the rack handle. Keep up the good work!

Ted / KC9LKE

I found pictures of it in Bear's photo section.


Rich

Carl, I think you got this backwards. The shorter the lead to a heatsink the better. The 1N5408 is rated to 75C @ 3A when the leads are .375" long, and soldered to a 20mm X 20mm X 1mm copper heatsink. The longer the leads the more we derate the diodes, not the other way around. Some examples:

http://doc.chipfind.ru/jgd/in5408.htm
http://sites.google.com/site/interfacebus/thermal-impedance/diode-lead-length-temperature
http://www.voltagemultipliers.com/pdf/Appendix%20B%20-%20Diode%20Thermal%20Analysis.pdf

The PCB designers need to provide fat traces big enough to act as a heat sink, and use short diode leads to get the heat from the diode to the heatsink. Longer is not always better.  ;)

Jim
WD5JKO

Nope, thats an absolute minimum length as a heat sink Jim. Mo is betta in a real world PC board or a hammy hambone perf board mount where the leads alone are the heat sink. Where would we be without perfboard anyway?

Here is the 1N5408's QRO fans big brother, note the 2 mounting procedure graphs.

Point an IR gun at either with a steady load and vary the lead lengths.

Carl

Ran that test about 35 years ago, but we didn't have an IR gun.

I use the 6A 1KV diodes for every PS here and don't worry about heat...

The price is close enuff to the smaller ones and they just laugh in the face of death... ;D 

T

Yep, and at .16 each in 100 qty at Mouser for MCC brand you can even afford to use them in place of a 1N4007 ;D

Are they THAT cheap now?  I used to pay a lot more at Silicon Valley - and was still happy...

I have a string of about 140 on my big HV supply. It's been FB for at least 20 years now.

T