815 Xmtr parts

Here's the collection of parts needed to build my transmitter (the power supply is separate). I'll mount the male 8 pin plug on the back of the chassis for power. The barrier strip is for metering points and for the key connection. I'll be able to connect in a plate modulator here also. In the final transmitter the two 25 watt pots will be...

read more "815 Xmtr parts"

Additional 815 xmtr Mod

Another feature missing from most pre-WWII transmitters is some sort of spotting capability. Two reasons drive the need for spotting capability today. First, with transceivers being the norm, operators rarely tune the band looking for a response to a CQ. If answering a CQ, you need to be close to on frequency. Operating in an open spot on the band is the second reason for a spotting switch. Choosing the right operating frequency/crystal...

read more "Additional 815 xmtr Mod"

Another layout

Here's another thought on layout ... move C2, the final plate tuning cap, from on top of to under the chassis. This frees up space top side and there is still enough space below for the parts around the 815. C2, a major shock hazard, is now safely under the chassis. I also found ceramic plate cap connectors for the 815. L4 is still exposed...

read more "Another layout"

815 Xmtr - Safety mods

Someone asked me about modifying a vintage design in the name of safety. Sounds like a good idea to me. I already modify vintage receiver projects to keep B+ out of the headphones ( see http://www.io.com/~nielw/onestep/onestep.htm ). I also try to keep transmitter B+ away from accidental touching. This design, unfortunately, has 500 VDC exposed on the final tank coil and C2. I plan a couple of things to to help. First a front...

read more "815 Xmtr - Safety mods"

815 Xmtr Parts Subbing

As I search for parts, the topic of subbing parts has come up, particularly for C1 and C2. Miniture 140pf dual section variables are called out for both of these. In my junque box I fine slightly larger (physically) parts and, for C2, only a 100pf dual section variable. I can probably work around the 100pf problem by adding two fixed 50pf caps to L4, a 80JVL plug-in coil. The physical size increase appears to be OK for C2 but...

read more "815 Xmtr Parts Subbing"

815 xmtr

I'm to the point of starting to layout my 815 transmitter. Here are a couple of figures from the 1943 ARRL handbook describing this transmitter along with a picture of my preliminary layout. My chassis is 3"x 8"x12" so I have a little more room. Good thing, since I didn't have the small size variable caps called out in the original design....

read more "815 xmtr"

815 transmitter

According to the 1942 ARRL Handbook the 815 requires less then 2/10 of a watt of drive. A 6L6 is rated for much more than that. The 6V6 has the same base pinout but lower rating. I'll switch over to a 6V6 for the oscillator stage. My power supply will deliver about 500 VDC for the 815 but I don't want to run the 6V6 at 500 volts. I'll need to somehow drop 500V down to about 150 VDC for the oscillator stage. Depending on current...

read more "815 transmitter"

6L6 - 815 three band xmtr

I've always been interested in the 815 based 50 watt transmetter that showed up in QST and the ARRL handbooks just before WWII. The 815 is a dual "beam" tube designed for UHF (150 MHz in 1940). I'm starting to plan a tramsmitter using an 815 as a push-pull final (as shown in Feb '41 QST) driven by a 6L6 tri-tet oscillator such as used by Millen in his 6L6-807 rack moount transmitt...

read more "6L6 - 815 three band xmtr"

Welcome

Welcome to my blog about my ham radio activities. Here's where I plan to "talk" about what I'm doing in the shack. Feel free to comment and/or email me if you see something of interest. 73, N...

read more "Welcome"

Grinding Transmitting Crystals

As I played with my 6J5/6L6 transmitter I saw that I had some holes in my 80 mtr crystal selection. I had several crystals at 3550 but practically none between 3550 and 3570. Before stable and well calibrated VFOs were plentiful, grinding crystals was a common activity. Military surplus crystals were obtained cheap and ground to the frequency of interest. I decided to grind some of my 3550 KHz crystals up a few KHz to fill in...

read more "Grinding Transmitting Crystals"

Alternator whine and tips on clean copy in your mobile.

Alternator WhineI want to revisit this problem, because there seems to be a lot of poor advice floating around on these pages. Let's start out with a few basic facts, but keep in mind this is NOT an alternator primer. If you need or want more data, the internet is your best friend.The average alternator's output is between 13.9 and 14.2 VDC....

read more "Alternator whine and tips on clean copy in your mobile."