Some Great Ideas of the Past!
February 18, 2021 ~ A Story in Conflict.
A story from today that is very much in conflict with the past and how right was separated from wrong. Today a well known person with a large cult like tribal following brazenly walks into a bank and robs it at gun point. There are 30 witnesses in the bank as well as 5 CCTV cameras. The man walks out of the bank with the stash and then is accussed of the robbery based on the evidence. His cult followers maintain he did nothing wrong. Their argument: he was simply removing the money from one location and spending it in another!
Ridiculous and improbable as that seems, his cult followers steadfastly maintain that position . Shame on you! It was always wrong and time to reconcile -- the bank robber is guilty!
The Dentron HF SSB Scout
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You Tube Video Too!
Homebrew CW Transceiver ~ N6QW 2/2021
One term often heard when we look at high technology products, or ones featuring elegant sophisticated designs, describes it all and that is "German Engineering".
My 1st encounter with German Engineering was my 1966 Volkswagen Beetle that I bought shortly after returning from Vietnam (the 1st time). The spare tire is located under the hood and to my horror after having only owned it for two weeks someone stole the spare tire! I went to the VW dealership during a lunch hour and purchased a spare tire and the sales person said you better buy the lock too! I was in a hurry and so said yes-- Total Bill $50 with the lock wherein I quickly headed back to work. Only this time I locked the tire in the car. After work I went about installing the spare tire lock and spare tire. Upon opening the special spare tire lock package -- I laughed out loud and uttered German Engineering.
So here was the special spare tire lock parts: A long bolt, a piece of high strength steel chain and a high quality padlock. The installation consisted of removing a bolt that went from the spare tire well to the frame. The next step was to insert that longer bolt that came with the kit through the end link of the chain and install that bolt in place of the one removed. You were to tightly secure that bolt so that it could not be hand removed (meaning you would need a socket or a wrench to unloosen it once installed).
The next step was to pass the chain through the tire metal frame several times and the set the tire into the well while also snugging up the chain. The Final Step secure the padlock to the other end of the chain! Boom no way to get the tire out without a key for the padlock. Simple solution and a secure tire = German Engineering.
But now back to ham radio and German Engineering. I read an article in CQ magazine about WWII German field radios. In one particular design (something beyond a Walkie Talkie) for use at the local force level there appeared a unique design. It turned out there were many of these radios that were deployed. So the designers thought about the issue of a vast number of field radios and their critical role in the conduct of warfare. This brought up the need for field maintenance and repair. The ever sought for quest, quicker, better, cheaper!
The solution -- these were 5 or maybe 6 tube transceivers and the design was the same tube was used in all parts of the radio. Thus neatly packed in the cover of the radio box was one spare tube that could be used in any socket. With the radios of this era -- a blown tube was typically on the critical failure path, Solution: A spare tube in every radio. German Engineering!
After reading this article Ii tried designing a 20M "toob" SSB transceiver using the 6AK5 as every circuit elemnet. I was up to 13 tubes. But if you check, the 6AK5 has a low current requirements for the filaments. So if you series the filaments for 12 VDC operation -- it was only a couple of amps for the entire filament supply. The 13th tube had its filaments in series with the pilot lamps. I actually got the receiver working; but then ran into some issues with the transmit side. Never did finish that project; but there certainly was a lot of metal bashing.
In line with our nostalgia theme I thought about Dual Gate MOSFETs and perhaps their use in a solid state equivalent of the German Engineered military transceivers.
So I went to my most cherished publication SSDRA and toured the circuits for any applications using DGM's which show the 40673. I am proposing using the 3N204 for which I have a small stock. I have tested circuits using the 40673 and swapped in a 3N204 --works!
To my surprise I spotted some circuits that have promise. These are shown above (All from SSDRA). So we could start with a Broad Band RF amp stage that I have designed using two J310's which is easily converted to the 3N204. I could use relay steering with this circuit so it would be the Rx RF Amp on receive and the Tx pre-driver on transmit. Check that block -- it has been done.
Somewhere in there would be a Band Pass Filter which feeds a 3N204 Mixer stage and then on to a 9 MHz Filter. Check that block. But we would need a relay or solid state switch to steer signals to a single pass IF amp stage. The alternative input is from a diode ring mixer that would feed the IF Module on transmit. One position is the BPF/Mixer that feeds the IF Module and in the second position the output of the Balanced Modulator feeds the IF Module. We do have the circuit for the 3N204 IF Amp stage so check that block.
Following the IF amp stage would be the Product Detector on receive and there is a circuit for a 3N204 to do that -- check the block. But on transmit a relay would switch over to another 3N204 Mixer stage that would take the 9 MHz SSB and mix that with the LO and run that through a 2nd BPF for the transmit chain.
In my Sudden SSB transceiver I do something similar only using NE602's. See www.n6qw.com and search for the Sudden SSB transceiver.
The LO and BFO are done with an Arduino Nano and Si5351. The Driver circuit show on the hand drawn schematic would be for the transmit driver stage. The final is an IRF510.
So just noodling here I think we have five 3N204's
- Receiver RF Amp Transmit Pre-Driver
- Receiver Mixer
- IF Amplifier (9 MHz)
- Product Detector
- Transmit Mixer
Other devices would be the 2N2219 Transmit Driver, 2N3904/LM386 Audio Stage. 2N3904 Mic Amp, IRF510 Final Amp. The LO/BFO comes from the Arduino/Si5351
A tip of the cap to German Engineering!
Dentron was on to Something!
Dentron out of Stow, Ohio at one time ruled the roost on Ham Amplifiers. Anyone remember or have a MLA2500 in their shack. During the early 1980's the world caught up and passed the US with new ham products that were cheap and caught our fancy. This caused many US Companies to try to move into arenas that were not their strong suit. This is like the glam movie actress who now was fifty, with sagging boobs, trying to star with a 20 something tanned hot hunk. It didn't sell well in Peoria nor Union, Missouri!
Dentron made that move from Amps to Transceivers and did have some interesting products; but likely was underfunded and just not competitive with the offshore "blinking lights and flashy knobs". Here is an example of one of the not so well known offerings from Dentron. It is called the Scout HF SSB!
BTW this is a current listing on eBay starting at $188.
Here is a tour of the innards. First it is a 5 Channel Crystal Controlled SSB Transceiver. Dentron used a basic SSB transceiver assembly (9 MHZ IF) purchased from a Japanese Manufacturer called Mizhou who made ham equipment. Their product line was walkie talkie sized SSB transceivers using VXO's.
Dentron bought the IF board then added 5 crystal channels to output in the 4 to 10 MHz range (USB Only) and inside that box is a 100 watt PA. The LPF as seen in the photos likley is insufficient to meet today's FCC specifications. The target market was like the CAP or industrial users.
It is barebones and lacks some basic controls like a clarifier, or microphone gain control. It looks like on the back panel you can make CW -- but likely not very good.
BUT they were on to something that could have been, had it been done today. Suppose you drop the crystal board and install an Arduino / Si5351 --- that would open up the spectrum. The channel selector location could be the encoder and using the encoder push button you could band change and relay switch the appropriate filters.
Modify the speaker grill to include a Color TFT right dead center and move the speaker back from the front panel with some spacers. Ditch the pilot lamp and install a USB/LSB select switch. Make the audio gain control a dual concentric pot with the outer ring being mic gain and the inner ring the audio. I would add a mini momentary pushbutton right below the meter as a TUNE button.
But my plan would have a few caveats. This is not ladies panty hose as one size does not fit all. Given where we are headed in the Sunspot Cycle I would make it a quad band rig to cover 40, 20, 15 and 12 meters. The 17M band was a concern because of the 9 MHz IF. With the N6QW Digital Adapter and USB, this opens up this rig to prime use for FT-8 for those so inclined.
BTW --you can find schematics of the Dentron MiniLX which was a 15 watt SSB/CW transceiver and it uses a similar board from Mizhou. For a lot of hams this is too hard (more out of laziness) so go to https://www.n6qw.com and there is a link to the Dentron MiniLX pdf so you can find it there. I find it hard to believe so many hams do not know that Google is their friend!
So for those who have never built a thing in their lives --this is your project! Jump in, solder your fingers together, burn a hole in the rug, smoke parts and place more orders to Amazon through the Solder Smoke blogspot link. This is reliving the past and it is your chance to enjoy that journey! [Caution homebrewing a HF SSB Scout could cause pedis plantis, dermitophitosis, baldness, crossed eyes, insane food cravings and borderline schizophrenia!]
So OK here is my version of the Dentron HF SSB Scout!
Special Commentary: There was another ham equipment manufacturer that offered a SSB Transceiver by the name of Scout! Yes, the Ten Tec Model 555 ~ Scout. It was essentially a single band (at a time) rig which used plug in Band Modules. This Scout variant had many innovative features; but could be costly if you purchased additional band modules.
Today the problem is that a Scout is sold with a single module on eBay; but it is tough as nails to find additional modules. There is a Model 555 on eBay right now for a reasonable price but comes with a 10 Meter Module. That won't be useful for another year or two.
73's
Pete N6QW