Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: need circuit for using 1Q5, 3Q5 or 3A5 (xmtr or receiver) or suggestions  (Read 742 times)
AK0B
Member

Posts: 371




Ignore
« on: April 15, 2019, 08:55:54 AM »

Many years ago I obtain NOS 1Q5, 3Q5 and 3A5 tubes with the idea I would someday build a battery operated QRP transceiver.  They are dual triodes with 1.4 v filaments and 90 VDC on the plate.  Listed as beam power.  Must be from the late 30's Huh

any suggestions or leads on some old circuits using them.

It appears no cathode.  So not sure how I would key them.

any references appreciated.

thanks,  Stan AK0B

Logged
AK0B
Member

Posts: 371




Ignore
« Reply #1 on: April 15, 2019, 09:01:42 AM »

correction the Q5s are pentode
Stan AK0B
Logged
G3RZP
Member

Posts: 1286




Ignore
« Reply #2 on: April 15, 2019, 11:10:29 AM »

One way is block grid keying with a negative bias source. Another way is to key the B- line. Or key the screen grid, although a negative blocking bias might be needed on the 3Q5 to reduce back wave. The 1927 ARRL handbook has references!
Logged
AK0B
Member

Posts: 371




Ignore
« Reply #3 on: April 15, 2019, 01:00:22 PM »

Thanks, G3rzp,  good suggestion.   I didn't have any handbooks that old, but did have a dusty arrl cd for the  20's.  It was very interesting to review the old xmtr circuits.

Some let the gird float and key using a grid bias and some let the grid float and keyed to ground.

Even ran across one that keyed the center tap of the filament. Don't think I will try that one.  Smiley

thank, 73 de stan ak0b
Logged
KB1GMX
Member

Posts: 1807




Ignore
« Reply #4 on: April 16, 2019, 08:43:16 AM »

The 3A5 dual triode at 155V will do 2W output on 80m.  Keyed plate is the usual arrangement.

The other two the 3Q5 and 1Q5 are the same tubes for ether 1.4V or the 3A5 2.8V/1.4V due
to center tapped filament.  They are beam power pentodes for audio output to about 400mW.
They might do more at 80M if pushed but not suggested.  They were for portable/battery used
as audio output.

What you have is an odd bunch and the 3A5 is a good RF tube for transmitters.

Best circuit i know of for tubes of the era is the September 1950 QST, The mountaineer a 80M
portable transceiver. If you are a memeber you can get it off the site.  However the that required
1R5 and 3 1U4 plus the 3A5 for a two tube transmitter and a 3 tube regenerative RX.  Good
news is the tubes are easily had and generally low cost and they have no appeal to the
audiophiles. 

Allison
Logged
AK0B
Member

Posts: 371




Ignore
« Reply #5 on: April 16, 2019, 07:59:49 PM »

Thanks Allison .  I got a copy of the article.   Nice looking unit.  The only thing the author left out was what pin number was what on the power key socket. Smiley   I will trace it out. I have all the tubes; about 20 years ago I stocked up parts which I thought would not be available in the future. 

Cleaver the way he adjusted for the antenna length. 

73,  de Stan AK0B
 
Logged
KZ4AK
Member

Posts: 13




Ignore
« Reply #6 on: July 23, 2019, 03:23:41 PM »

Brings back memories...  I built a transmitter using a 3A5 many many years ago when I was a kid (so don't have the schematic).  One section was the oscillator, the other was an amplifier.  Transmitted AM using a scrapped tape recorder audio section.  This was pre-ham, I was about 15 at the time.  It was on 11M (CB) and made contacts over 50 miles away.

Woody - KZ4AK
kz4ak.com
Logged
KM1H
Member

Posts: 5309




Ignore
« Reply #7 on: July 23, 2019, 04:39:13 PM »

The 3A5 was popular for bicycle mobile magazine articles in the 50's as were several others of the 7 pin miniatures. RCA listed the 3A5 at 2W out at 40 mc and was still fine at 6M. May 1942 introduction and used in WW2 Walkie Talkies

https://frank.pocnet.net/sheets/049/3/3A5.pdf

The earlier octals and loctals were more common in the shack due to size and fine on the HF bands for RX and TX.

Carl
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!