This is a updated collection of easy to build projects for radio amateurs and swl's. See all my projects in the OLDER POSTS down this blog.
Have fun.
73' John

Mutual respect is the key to global peace.....

Saturday, July 29, 2017

Antenna switch .

By means of a Apem DPDT on-on 15A toggle switch a reliable 100 Watt HF antenna switch can be made with 2 advantages.
1: the switch points to the connected antenna.
2: the non connected antenna is grounded.
The picture shows the switch from behind.



Monday, July 17, 2017

IC-7300 preselector idea.

The IC-7300 has a signal overload problem. A preselector can be an option.
L1 - T80-2 .  L2 - T68-6 .  L3 - T50-6 .  T1 - T2 are 1:9 transformers. By adding a 470pF capacitor to ground between T2 and the polyvaricon the overall swr drops to a verry acceptable levell.


Sunday, April 02, 2017

Voice keyer ( CQ parrot )

Calling cq in ssb with only 5 Watt can cause a sore throat....
Although in production for severall yaers this exellent kit BX-184 from Box 73 is still a must have for the QRP operator. Link
Easy to build high quality kit that provides 60 seconds voice recording and a strong punch to the modulation . I had to reduce the mic. gain to 25% on ssb and 15 % on fm/am at the FT-817.
This kit is also available with a extra MH-31 type mic. enabeling the use at other transceivers with 5V or more at the mic. cable. The red dot marks the fst button that controlles the functions,

The modified MH-31 mic.with pcb




Tuesday, March 28, 2017

Coax to pcb the easy way

 

Soldering a coax braid in to small pcb holes can be verry stessfull. Teflon coax is the best choise.
Here is the solution

Friday, January 20, 2017

EFHW antenna for 40-10m qrp

I had a BN43-202 core in stock and decided to try to create a small QRP EFHW transformer from 7 - 29 MHz. As you can see in the plot the swr is verry flat from 40-10m so a capacitor at the input is not needed. A 3300 Ohm resister to ground was used for the plot but at 1700 Ohm the transformation is near perfect. Don't use thin antennawire for this rises the impedance of the antenna. 1.5mm is a minimum . With just 20.3m wire this makes a nice 40-10m antenna. You can also use the 34uH coil of the endfed down this blog to create a compact 3 band atenna of just 12m long. 10 Watts PEP is the max. power here. Be carefull, each pass is 1 turn here. A test with 2 transformers back to back showed a power loss of about 18% on 20m. I used 0.7mm transformer wire .




Disclaimer:I'm not responsable for any damage due to improper reproduction of my projects.

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