Support QRP CoA Everywhere

Saturday 30 January 2010


Just applied for the 500kHz NoV.

In the shack building a 500KHz version of the PA0SE field strength meter for 500kHz which is basically a DC RX with audio and DVM readout.

Will use DVM M-830 B that can sense to 200uA and 2000uA.

Mixerwill be SA612 or TFM-335 (Mini ciruits, because I have some!)

TL072 Dual op amp

The LO still making up my mind but think a colpitts oscillator might be easiest. Either LC type or use a 500KHz ref crystal and pull it a little. Otherwise 4MHz colpitts with a PNP buffer and then divide by 8 using perhaps a 74HC4040.

For the front end will use an LF preamp/selector for 500KKz using J310/2N2222A and the preselector is simple LC filter using 1mH axial choke and 500pF capacitor.

I will use a ferrite rod, for the input, and as I have a couple I might try and use a superdrug ( for GQRP homebrew silliness) ferrite rod and add additional winding to the MW coil suitable for 500kHz. Will dip the coil for 500KHz.

No circuit at moment but I'll write it up.

It's snowed last night and it is cold outside the shack and the cat helped select the circuits.


Unknown said...

When this page cane up I thought "500KHz is a funny name for a cat."

M1KTA said...

Cat's called "Pud". When in the shack he has a habit of sitting on what I want to work on.

Anonymous said...

Pud needs to meet Daisy at


M1KTA said...

Thanks Charlie,

What drives Pud nuts are the birds lined up in the mornings on the G5RV, when it is up. He will pace up and down the shack roof... I am sure he has thought more that once about climbing up the 450 ohm open wire feeder hihi...

Don't forget G6ALU's cat who is a skilled search and pounce contest PIC-A-STAR operator...

Ricardo - CT2GQV said...

Hello, What's the name of the book with the spiral back? Look's interesting.

M1KTA said...

That is the data Data Book for Homebrewers and ORPers by Paul Harden NA5N. He gave me my copy at the GQRP rally in Rochdale 2006 or 2007.

Every now and then copies appear.

I update the deives pages adding some modern devices and also a section on SMT components. The sections on old rigs I removed (and saved) then I borrowed a spiral punch from a place I did a job and made some extra pages and then reconstructed the book.