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Author Topic: 80 and 40m Communications Tube Reciever  (Read 596 times)

ZS5WC

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80 and 40m Communications Tube Reciever
« on: August 16, 2021, 03:33:36 AM »

 :)I want to build for Nostalgic purposes a mostly Tube Communications reciever or transciever for 80 and 40m with readily available parts, coils that can be duplicated, no Denco coils!..
I should have 455K/C cans.
Been looking at the 2X4+1 and DCS-500.
Crystal filter is a must.
Any other suggestions and where to find project details?.
I want to build a novice station for SSb and CW, mostly for SKN.
73de William
ZS4L / ZS5WC
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KM1H

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Re: 80 and 40m Communications Tube Reciever
« Reply #1 on: August 16, 2021, 06:54:08 AM »

ARRL members have access to all the old QST and Handbooks; anybody can join. CQ archives are online and they had quite a lot of good articles into the 60's or so.

Carl
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W2EAF

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Re: 80 and 40m Communications Tube Reciever
« Reply #2 on: August 17, 2021, 07:54:58 AM »

There are 3 books I highly recommend for what you are looking to do. The first 2 are free to download from The Internet Archive at archive.org.....1968 ARRL Handbook and 1959 Radio Handbook. The third is from qsl.net....How to Become a Radio Amateur (1970). It takes a bit of searching but these 3 are excellent resources...I have hard copies of them all and have found them invaluable for building "vintage" projects.
Rob W2EAF
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G3EDM

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Re: 80 and 40m Communications Tube Reciever
« Reply #3 on: August 17, 2021, 08:17:39 AM »

You may find this recent eHam thread useful:

https://www.eham.net/community/smf/index.php/topic,133797.msg1231600.html#msg1231600.

Few of the simpler receiver projects use an IF of 455 kHz, so you may need to find (or build) IF transformers for a different, usually higher, frequency.

There is huge difference in complexity between the 2X4+1 and the DCS-500, but I am sure you know that already.

Finally, none of the Novice-style building projects include SSB transmission, which is understandable given the complexities involved in building a sideband TX.

Edited to add: The transmitter side of the building project is perhaps easier to figure out. I recommend these ARRL publications for all aspects of building a vintage Novice station:
  • The 1968 edition of "How to Become a Radio Amateur".
  • The 1963 edition of "Understanding Amateur Radio".
  • The 1963 ARRL Manual.

73 de Martin, G3EDM

« Last Edit: August 17, 2021, 08:23:14 AM by G3EDM »
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G3EDM

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Re: 80 and 40m Communications Tube Reciever
« Reply #4 on: August 17, 2021, 09:05:50 AM »

For what it's worth, the building of my Novice station is documented here:

https://www.eham.net/community/smf/index.php/topic,133657.msg1230085.html#msg1230085

This is probably too elementary for your project, given that you are already heading toward building a superhet receiver and my receiver is a very simple regenerative set, and your subject line specifies "tube receiver" while mine is solid state. But it does give a general idea of what it's like to build vintage ARRL projects.

73 de Martin, G3EDM
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WB6BYU

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Re: 80 and 40m Communications Tube Reciever
« Reply #5 on: August 17, 2021, 06:47:05 PM »

Quote from: ZS5WC

I want to build for Nostalgic purposes a mostly Tube Communications reciever or transciever for 80 and 40m with readily available parts, coils that can be duplicated, no Denco coils!...

I should have 455K/C cans...

Crystal filter is a must...




This might make a difficult combination, unless you have a
good source for the WWII crystals in the 455 kHz range.

It is much easier to build acceptable crystal filters using standard
off-the-shelf frequencies like 4.433 MHz, 6 MHz or 8 MHz, so
unless you are planning a double conversion design, combining
these two features will make things much more difficult.

(Although the double conversion isn't a bad approach in this
case, especially if you keep amplification at the first IF to
a minimum.)

There are ceramic resonators for 455 kHz that can be used
in shunt to make filters - a design using 500 kHz resonators
appeared in Technical Topics, and that might be used
with your 455 kHz transformers, although the load impedances
might not be ideal.

A number of solid-state designs used 10.7 MHz IF transformers
with additional shunt capacitance to tune them to lower
frequencies, sometimes down to 80m.  If your junkbox includes
some old FM broadcast receivers, this approach might work.

If you choose an IF in the 5 - 6 MHz range, then a single VFO
around 2 MHz would only need a small change in frequency
(or possibly none at all) to cover both 40m and 80m, assuming
you don't mind the tuning working "backwards" on one band. 
Lower frequencies are often easier for designing narrow CW filters,
while wider filters for SSB may be easier in the 8 - 10 MHz range.

Remember, while audio filters are commonly implemented using
op-amp IC chips, there are designs using tubes as well, as well
as passive designs (some using the old 88 mH toroids).

Coils for tuned circuits can be wound toroid cores (if that doesn't
spoil the desired aesthetics, of course), which are relatively easy
to adjust for the number of turns on various links.  The coils
themselves won't be easily variable, but they can be tuned with
trimmer capacitors if you don't have slug-tuned coil forms
available.  (You can always hide such modern items inside the
cases from junked transformers.)

In the end, the decision will probably be based on what parts
you have on hand or can get easily, what features you want, and
the desired aesthetic.  For covering both the CW and SSB
portions of the bands (especially the Region 2 80m band from
3.5 to 4 MHz), tuning rate becomes more critical, especially for
SSB, or CW with a narrow filter.  That might require separate
bandset and bandspread controls, multiple VFO tuning ranges,
or cascaded vernier drives.

While AGC is nice, I spent my novice years riding the RF gain
control (the BFO signal leaked into the AGC circuit), which
simplifies things.

Do pay particular attention to the various mixer products when
choosing your IFs.  I have a bunch of 10.7 MHz crystal filters
that seemed like they would be great for building SSB radios,
but on 40m the second harmonic of the oscillator is in the
desired output range, so filtering becomes a nightmare.  (And
operating on 21.4 MHz is a real challenge!)

KL7CW

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Re: 80 and 40m Communications Tube Reciever
« Reply #6 on: August 19, 2021, 10:47:26 AM »

BYU has good suggestions.  I have used "standard" inexpensive crystals for both filters and BFO use.  For one project I bought probably 25 crystals in the 7.xxx MHz range for probably 15 or 20 dollars.  I sorted them, and found several groups of 3 or 4 crystals close in frequency (probably less than 15 Hz difference) and a few further removed crystals.  My variable BW filter worked fine and I found an acceptable BFO crystal in the assortment which only needed a bit of capacitance or inductance to zero it to exactly where I wanted it.  For my portable rig the performance was very acceptable, but not up to par with a "proper" HF receiver.  At the time I managed without a spectrum analyzer/tracking generator, but it took some time.  For best performance you should pay careful attention to the input and output Z of the filter.  I believe I got these crystals at Mouser and think they had others in the 3 to 8 MHz range.  Before you go too far in your design, I would go to one of the on line mixer spur calculators.  All mixers have dozens of output frequencies, and some of these may not be acceptable.  Buying a filter is probably what most sane folks would do, but some crazy hams like myself do things the hard way !!              Cheers,    Rick  KL7CW
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VK3YE

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Re: 80 and 40m Communications Tube Reciever
« Reply #7 on: September 14, 2021, 05:04:32 PM »

:)I want to build for Nostalgic purposes a mostly Tube Communications reciever or transciever for 80 and 40m with readily available parts, coils that can be duplicated, no Denco coils!..

One possibility is some form of 'band imaging' superhet.

Here you have the IF around 1.7 MHz and the VFO around 5.3 MHz.

This is discussed here: http://dpnwritings.nfshost.com/ej/goodman_receiver/

The advantage is that if you get the IF and local oscillator combination right you will not need to switch the local oscillator.

Band changing just involves peaking the front end at 3.5 or 7 MHz. 

Something else to consider is doing it the other way using an IF around 5 MHz and VFO around 2 MHz.

Though the mixing scheme is a little different but there is a benefit in using cheap 5 MHz region crystals to make a good filter.

But I wouldn't choose an IF exactly 5 MHz due to the risk of breakthrough from WWV. And you might have birdies due to VFO harmonics.
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W9GB

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Re: 80 and 40m Communications Tube Reciever
« Reply #8 on: September 15, 2021, 08:13:31 AM »

Quote from: ZS5WC
Nostalgic purposes a mostly Tube Communications reciever or transciever for 80 and 40m with readily available parts, coils that can be duplicated.
Greg Latta, AA8V
https://www.frostburg.edu/personal/latta/ee/ee.html

John Seboldt, K0JD
http://www.seboldt.net/k0jd/

Tom Nickel, KC9CEP
https://www.glowbugs.info/2010/02/big-nick-and-cydecos-glowbugs-radio.html
YouTube Video
https://youtu.be/F_0DDkXPd60

John Kelly, N3GVF (SK)
Master Radio Craftsman
http://www.k2tqn.net/oldradio/arrl/2000-07/index.html
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KL7CW

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Re: 80 and 40m Communications Tube Reciever
« Reply #9 on: September 15, 2021, 06:10:48 PM »

William, your project sounds like it will really be interesting and fun.  I have a few suggestions which may make it easier to get a working station.  First of all I would build either a separate receiver or transmitter and get it working first.  Play with it, get it on the air, and modify it.  When all is well go for the next item and get it working separately.  Then put the pair on the air.  You can even go from TX to RX with one or more switch.  That was the way most of us did it back in the 50's.  I built many separate receivers and transmitters and most eventually worked fine, or were used for parts on my next project.  However several transceiver projects from 40 or more years ago are still in a box probably never to be completed.  For you project you could consider battery power, if the tubes are still available. The ones I used were not miniature but were designed with fillament (sp ?) not a cathode and could run on one or two D cells for a long time and B+ of anywhere from perhaps 22 to 45 volts.  I think they had numbers of something like 1T4, 3S4, 3A4, etc if my memory is correct.  For TX some of these tubes only could put out perhaps 1 or 2 watts if memory is correct.  Back in the day they worked fine.  There are even very small tubes, not much bigger than a pen cap, but I never had experience with them.  They were used in spy radios I think.  Enjoy your project.  I like to build mine on bread boards, get each stage and unit working, then finally assemble the whole receiver in your nice cabinet.  Others even build each section, IF, AF, etc. on a small board or chassis, then hook all the units together in your big chassis or cabinet.  Leaves the possibility of further improvements.        Cheers,   Rick  KL7CW
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G3RZP

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Re: 80 and 40m Communications Tube Reciever
« Reply #10 on: September 17, 2021, 04:51:50 PM »

The ARRL Handbooks of the mid 1950s a had a couple of designs of 5 tube two band double conversion superhet receivers. A good start there...

vy 73

Peter G3RZP
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