Turning the 6DC6 into a 80m preamp for a reciver.

Discussion in 'Homebrew and Kit Projects' started by KC9OXP, Feb 28, 2009.

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  1. KC9OXP

    KC9OXP Ham Member QRZ Page

    Does any one know the proper way to turn the 6DC6 into a 80 preamp for a receiver?
    I have a few of these tubes and i would like to finally use one and my tube transformer. I would like it mostly for 80M preamp. If possible to also cut down on some static. All parts needed I would have to scavenger or make. It would need to be able to handle the full range of the 80M and its modes.
  2. WA9SVD

    WA9SVD Ham Member QRZ Page

    What sort of receiver are you using? A preamp on 80 Meters is usually a disadvantage, and will certainly not help REDUCE static; it will only make the static (as well as signals) moch louder. Most receivers have more than enough sensitivity on 80/75 Meters, and a preamp will not help in the least.
    Static is the bane of the lower frequency Amateur bands, so you're not alone. One possible circuit might be to Google "noise blanker" which MAY help in your case.
    Last edited: Feb 28, 2009
  3. K9STH

    K9STH Ham Member QRZ Page

    Although, as has been pointed out, a preamplifier is unneeded in like 99.999 percent of the situations on any receiver built for HF in the past 30 or 40 years, if you really want to use a 6DC6 then go to the Collins Collectors' Association website and download the manuals on the Collins 75S-1 and 75S-3 series receivers. Those receivers use a 6DC6 as the "front end". The URL for the manuals is


    Glen, K9STH
    Technical Adviser Collins Collectors' Association
  4. KL7AJ

    KL7AJ Ham Member QRZ Page

    If you're dying to put your lonely tubes to work, you might try a unity gain PRESELECTOR, instead. As emphasized already, you don't NEED any more gain, but you can always use a little more front end selectivity. You can configure your tube as a Cathode Follower (which actually has a little bit of signal LOSS) behind a very high Q tuneable tank circuit. I used this system extensively when I operated 160 near a 50KW broadcast station.....never even knew the station was there!

  5. KC9OXP

    KC9OXP Ham Member QRZ Page

    The receiver is a Hallicrafters SX-117. I have just recently restored it and got it 90% functioning, the other 10% is 1 dead band and 1 miss aligned band, I supper glued plastic rods to the iron slugs and 2 of the bands got glued shut. So till I get more proper slugs and a drill its going to stay that way. It all ready uses a 6DC6. My main issue is that I cannot put up a proper antenna do to the size and my current place of residence. So some guys are strong others are very weak as expected. I like to DX receive with it. I use a long wire in the attic and I couple it to the center conductor of my coax that runs 100' to an out side J-pole for 2M. Then I connect the receiver input to the outside braid of the coax. This setup is quite effective for multiple band receiving. What I am wanting to do is connect the attic line to the 6DC6 then connect the out put of that to the center conductor again. Also experiment with different setups.
  6. KC9OXP

    KC9OXP Ham Member QRZ Page

    How would I go about doing that? I do have a hand held HF receiver that always overloads with nearby local am broad cast.

    Also if you use ceramic capacitors instead of a polypropylene capacitor does it matter if the circuit calls for the poly?
  7. W0BTU

    W0BTU Ham Member QRZ Page

    May I suggest a W7IUV preamp (http://w7iuv.com/preamp/preamp.html). It uses a 2N5109 and works just great from 160 to 10 meters. I have a similar one using a TRW LT1001A CATV preamp bipolar, and you can't beat it, in my opinion.

    I'm partial to tubes, too. My Collins S-Line uses a number of 6DC6's.

    But for practical use (that means giving up our emotional attachments to tubes when ncessary), a solid-state broadband preamp like W7IUV's can't be beat.

    73 Mike
  8. KC9OXP

    KC9OXP Ham Member QRZ Page

    I saved that link. Right now I am too broke to buy extra parts and I dont have that transistor in my stock, or a suitable counter part. Im an 80's child so tubes are just a fascination to me, and I have about 20+ new old stock of them that my grandfather gave me.

  9. W0BTU

    W0BTU Ham Member QRZ Page

    Hi Mike,

    The link there has just changed and that link is 404. Just go to http://w7iuv.com/ and click the proper link in the left frame.

    I see you're currently jobless. That kind of puts a damper on buying parts, doesn't it?

    Well, I admire anyone who likes to build his own stuff. I don't have any 2N5109's, but I do have ferrite cores for the transformer in the circuit. It's not the same core as he has, but I'm pretty sure they will work.

    If someone else will donate a 2N5109, I'll donate the ferrite. :)

    73 Mike
  10. KC9OXP

    KC9OXP Ham Member QRZ Page

    Got the main page now. Yup being jobless is a drag. No work around here. I mostly scavenger for parts. What I spent most of my time doing today, now I have butter dish of odd ball parts to sort out and classify. If I get those 2 parts donated I have the other parts.
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