I was wondering why the Softrock TXRX had just 3 close bands (mine 10-12-15m). Now I know there were good reasons for that!

Suggestions based on experience and good practice are all good. It is my experience however that some fairly simple measurements can and need to be made in order to confirm a layout.

First, simply connect up the input and output on a completely unpopulated board and measure the attenuation. If you find less than 80 dB of attenuation at any frequency below 100 MHz, you are probably not going to like the end result. I would then add the relays and check it again. At this point your attenuation needs to be at least 70 dB. Add all remaining components except the filters themselves and check it again. Finally, one at a time, add the filters and check after each one is added.

If, at any step in the process, your input to output crosstalk gets higher than -60 dB, you are not going to be very happy with the outcome. Note all of these measurements are made with the relays deactivated so there is no actual intended path between input and output.

When working on a similar project with Tony Parks for an all-band Softrocks RXTX our first two prototype filter boards measured less than 30 dB isolation between input and output. And we thought we were following good layout and RF principles.

BTW, on the Softrocks project we finally got there........ only to realize that the radio would never make compliance goals without a similarly switched interstage filter prior to the RF drive chain. At that point we had pushed the cost of the radio beyond the target and the project was scrapped.

My bottom line reaction is: layout as best you know how but test, test, test.

WA8TOD

RE LPF Board?
above as example page.. I can't be? bothered with time of? doing a Cut and paste just to make up a picture of something you know about.. These Green headers must be available all over surely and the plugs to fit em.

If sending signals and power over from main board (using the decoding scheme) you might like to make sure you can
get 12V, zero rail and the three bit signals over on a green horizontal? 5.08 pitch header? (this assumes 5V for the decoder generated on the PCB ).. then the user just makes up a cable that picks up all the points on the main board .. direct soldered, Cable? fixed in some way to main PCB and then just plugs into daughter board.? ?Saves people mixing voltages if they pull the boards apart and then reassemble them as such headers are polarised. .......

开云体育

Nick
1. Wired OR diodes used for Relays J1A B? great idea. and I can see you seem to have allowed for relay contacts being opposite sensed. Ie J1A B set is active when Energised and Energised is out of cct.
2 . you have three signals and because of the wired or you have effectively four states without using a decoder. So how is the R5 to be energised. ?? Is it there for case of special software mod plus I2C or ....?

3. You need to define the relay functions.? From a Sota point of view it makes sense that J1AB set is a 20/30m Filter. Ie NO relay energised when working 20m.
then J2 becomes 80 m. then J3 40m? and J4 becomes 15/17 and J5 becomes Ten m after some magic.
4. You have allowed? spike suppression diodes for all relays except first pair. Forgotten or? there is a reason. ??
5. Kees Talen is also talking of a Five relay board design.? With Decoding to be done Off board somehow. Perhaps you need to check up his thoughts.
6. Given? 5.? I would suggest that you allow sufficient pads for a? 74HCT42 decoder and? a 78L05 to power it.? These pads could be on basis of wired chip mounted as SM (legs become feet at 2mm up from tips) so the cost of the holes is not there.? You will also need 4 off BS250 P Mosfets? (simplest solution and they are cheap) to activate the last four relays sets.? The points where the Wire goes off to the Wired OR should be? a through hole rondel.? All this could be squeezed in up T LHS of board as presented without much increase in board space.

The final wiring could be done with? Cat E wiring cores stripped out for those who wanted to go this way . I would suggest the following mapping? 000 as input to decoder? means nothing.? Same for 001.? 010 activates relay set 2 and also energises J1AB via wired OR? .? ...etc all the way to 101. If you use PNP transistors, you will be up for one extra current control resistor per bit.? BS250s are logic level Mosfets? RDS on approx 14R.? Futurlec.com have? them Rockby in Australia list them but have to order them in.?

The mappings and Relay usage have to be defined up front or? the software will be a schmozzle.?

Is the current voltage going to K1 coil 12V .. the schematic calls it Tx voltage. It appears likely to be 12VDC but without details of the guts of the Raduino I cannot be sure.

Just to exclude you weren't listening the WWV. You also can use the other references at 5 and 15Mhz. Usually when I calibrate something as a double check I use these references too and a shortwave broadcast using ssb

Another user installed the KD8CEC software and found it to be an
improvement.
Changing the pull up will not help the issue. The factory code is
slow in
recognizing keying.

Allison

This might be a possible fix:

_._,_._,_

开云体育

开云体育