Solid stating a tube RX

[W1DAN]

Hi:

So many years ago I solid stated a basket case prewar HRO. The radio worked, but I could not get the local oscillator to track, and shelved the project. Recently I decided to Google a bit to try to discover if someone had more successfully solid stated an old tube ham RX. I came across two articles. This first one is an extremely well written thesis from a guy who was in Naval Post Graduate school in 1974. The ICs used are pretty dated, but his thoroughness is impressive:

https://calhoun.nps.edu/bitstream/handle/10945/17239/solidstateconver00steu.pdf?sequence=1&isAllowed=y

The analysis and conclusions sections are worth reading. Remember that this guy typed all the pages!


The second article is about a ham who solid stated a Hammarlund HQ110.

http://www.eham.net/articles/30168

So for interest, has anyone done this and got the LO to track? How did you do it? Wonder if anyone used any form of  cascode oscillator to try to reduce the gate capacitance? Not sure if I will get back to my HRO, but it is interesting to read about this idea.

73,
Dan
W1DAN

[N2DTS]

Why do it?
My tube home brew receivers work better then any solid state ones I ever tried.
What are you looking to do it for?

[W1ITT]

Dan..
Back in 1977 in the April and September issues of QST there were articles by Howard Sartori on making solid state tube replacements for the Drake 4-line equipment.  As I recall, the stinker was a particular high voltage FET that was difficult to obtain at the time.   With the improved range of FETs available now, you may be able to reverse engineer his work into something of use in your current project.  I had looked into building a few of them at the time, but gave up due to component sourcing problems.  I still think it might be fun to do, but it's a bit further down on the priority list.  If you build the "tubesters", as they were called, on plug-in bases you can return the rig to original condition if you don't like the results.
Years ago, I stuck an FET into a Collins PTO, lowered the B+ volts and it worked stable as a church.  It's fun to try.
Norm W1ITT

[W1DAN]

N2DTS:

I enjoy tube receivers immensely. The SS HRO was a learning experience. So in the end, I did it for technical curiosity and to see if I could "improve" performance. For an HRO-60 I own, I sometimes just pull the 6V6's and clip lead a SS audio power amp to the volume pot. Cuts the power draw by quite a bit and easily restorable.

Hi Norm: Yes I know about the Tubesters, and have come across the documentation about them online. The most successful was a 6AK5 replacement.

Just looking for other people's experience.

Thanks,
Dan

[N2DTS]

I was just wondering if it was a particular problem you were trying to solve.

[steve_qix]

Hi Dan,

I have solid stated two BC-1004s and an HQ-something, along with some other misc. receivers.

I did not have great difficulty in getting the L/O to track properly.

These are however, non-trivial projects in general.  Essentially, you are building a receiver from the ground up, using the existing passive components as a foundation.

Everything works differently than in the tube world from the AGC to the mixers to the detectors.

This is not to be discouraging.  The results of both of the BC-1004 solid state conversions are very good, and in fact one of these receivers is my main station receiver.  The other is in the kitchen area of the main house - both are used every day.

I used dual gate MOSFETs in the front end and in the mixer stages.  The IFs are jFETs.  Other circuitry is comprised of op-amps and bipolar transistors.

In my case, I kept everything high impedance, because that is what the RF and IF transformers were designed for.

Certainly a worthy project!

[ka1tdq]

Yeah, I solid-stated a receiver once (the rectifier tube), but then I got lazy and left the rest alone.   

So a solid state BC-1004.  That's probably the only one in existence.  I must admit that I'm jealous.

...by the way, baby #2 just arrived.  I should probably go change a diaper or something.

Jon

[W3GMS]

Yeah, I solid-stated a receiver once (the rectifier tube), but then I got lazy and left the rest alone.   

So a solid state BC-1004.  That's probably the only one in existence.  I must admit that I'm jealous.

...by the way, baby #2 just arrived.  I should probably go change a diaper or something.

Jon

Congrats Jon, not for putting SS rectifiers in but to you and your wife on your new child.

73,
Joe-GMS

[KD6VXI]

Congratulations John!

I've got two myself,  10 and 11.  My 11 year old digs tower bases for me.   He did a 7 foot deep,  2 foot square hole in 5 hours one day.

My younger one is the athlete,  until dad goes in the workshop.   Last year,  he built a single and 3 way light board to demonstrate how switches in houses work.

This year,  where going to dead bug a spark gap!

Kids,  love em!

--Shane
KD6VXI

[ka1tdq]

Thanks guys!

This one's a girl, and I'm not holding out too much hope that she'll be interested in ham radio.  The boy, however, I'm hoping he builds circles around me when the time comes.

By the way, people talk about converting old receivers to solid state.  But has anyone ever considered converting a modern solid state transceiver to tubes?  How about the Icom IC-7851?

Jon

[W1DAN]

Hi Jon:

Congrats on your little ones (i.e. harmonics)!

On modifying a SS rig for tube service, I think we can do this open-source and crown funded. I propose a push-pull set of 6AK5s in the front end and a 7360 for the mixer. For the RF power stage, I propose a broadband RF stage like Central Electronics. May need a set of 813s. :-)

Dan

[WBear2GCR]

One can get "pentode-like" performance from what was developed by Western Electric, produced by them and then Teledyne as "Fetron".

The basis for the design is documented both by articles found online (Teledyne articles mostly) and by looking up Otto Shade's work.

I think one can still find Fetrons on ebay and the like (someone sold about 300pcs a while back!) but they are mostly 6AK5 type and some are 12AX7 type. Western used them to replace tubes, to reduce maintenance costs, but then the whole shebang became obsolete anyhow... ha!

Dan, wonder if you can refer to the specific oscillator circuit schematic, and what you did? Might be interesting to see what that is.

                     _-_-bear