The Organic 5Watter VCXO Transceiver's Development History
Based on the 1Watters.
The 5Wxx is an offspring of the 1Watters, which was developed in mid-2015 at a suggestion from Chuck Adams, K7QO.
Chuck told me that he could use a code practice oscillator for teaching/training/class educational work.
Two days later I suggested a 20 Meter 1Watter which would use a dummy load to transceive in a classroom.
We ended up creating a VCXO transceiver with an IF of 6.00 MHz and 8.084 for the VCXO (both surplus xtals from ebay).
The band span was small, only 14,055 to 14,062 but good enough to cover the QRP freq and useful in the classroom.
With the success of the 1W20, we developed 1Watters for all nine HF bands, 10, 12, 15, 17, 20, 30, 40, 80, & 160 meters.
This required the purchase of over 10,000 crystals, most of which had to be manually matched for use in band pass filters.
Over 1000 1Watters were produced in the next 2-3 years... and we ended up with an abundance of matched surplus crystals.
What to do with surplus matched crystals? Create 5Watters :)
To keep the cost of the 5Watters low, I had to find a source of inexpensive RF transistors.
I did not wish to use FETs, probably because I have a phobia with matching, loading and exploding parts.
The old CB transistors are getting more expensive and anyway, most are fake Chinese parts sold on eBay.
By accident, I found that the surplus 2SC5706 transistor can do a great job configured as a pair of push-pull finals.
The FT of the 2SC5706 is 400 MHz, capable of more that 5 Watts RF output each, up to about 30 MHz.
The issue with the 2SC5706 is heat dissipation...it is a Surface Mount Device where the tab is usually soldered to a PCB.
To dissipate the heat, I decided to solder the final transistor tabs to a copper strip base available from GeorgiaCopper.Com
I created a dozen Copper/PA Assys; only one suffered from over-heating due to multiple attempts to orient the transistor on the copper.
Testing proved the PA Assys to be a success. Only once did I blow the finals; I powered the transmitter with no load on the output
and POOF...all the smoke came out; seems I forgot to install Zener Protection in the output circuit...now fixed.
In my attempt to remove/replace the finals in the PCB, I came up with the brilliant idea to use sockets for the finals and
the stupid idea to use my surplus stock of cheap 8 pin DIP sockets that could be cut up to make two 3-Pin Female Sockets.
The result was that the PA Assys made a sloppy fit in the the sockets. Per Chuck, K7QO, he said..."I use standard commercial 3-Pin Female headers".
Duh...Thanks Chuck...the true 3-Pin Female headers hold the PA Assys securely...very nice to be able to replace finals with no desoldering !!!
Chuck also suggested that soldering Finals to Copper may not be a good idea for novice hams/technicians.
I found that a very common half inch Aluminum Heat Sinks (eBay) could be securely connected to the small metal tab on the 2SC5706
by using a lock nut with a free spinning washer.
The Aluminum Transistor combination worked well but I think the Copper Transistor combo provides lightly better heat sinking. (YMMV)
The 5Watter Kits will include the Aluminum Heat Sinks; An optional Copper Heat Sink Kit will be available at kitsandparts.com
The 5Watters for 20, 30 and 40 meters are all capable of over 5 Watts RF output at 12 volts. The 5W17 is able to produce 5W but only at 14 VDC.
My initial plan is to build 500 kits; 50 for 17M, 50 for 30M, 170 for 20M and the rest for 40M
What makes the 5Watters Organic?
Organic is a sales/marketing term used to increase profits and sales.
I use the term to designate that the 5Watters are all analog (not digital)...and increase sales :)
73, Diz, W8DIZ, 7 July 2019