I had hoped to use this handy and cheap little frequency counter to add some glowing Juliano Blue to the frequency readout on my Quarantine Hodgepodge rig. I've used these boards with my BITX20, my HA-600A, and with my DX-100/HQ-100 rigs. But guess what -- these boards do not work with the BITX40 module board that is the heart of the Quarantine Hodgepodge. And the reason why is interesting.
Here is what happens: First, you plug in the IF frequency of your rig. In my case 12 MHz. You connect your VFO output to the signal input on the PLJ6. You power up the PLJ6. You then have to select one of two IF frequency options. One of these options ADDS your IF frequency to whatever it detects at the signal input. In my case, for a 7.2 MHz signal it would detect a VFO signal at 4.8 MHz. If it were to ADD this signal to the IF freq, it would readout 16.8 MHz. And it does. But obviously that is wrong. So you go to the other option -- this one SUBTRACTS the designated IF frequency FROM whatever it finds at the signal input. So here we get 4.8 - 12 = -7.2 Almost perfect right? But here is the problem: The PLJ6 can't handle negative numbers! So it displays 000000. Not helpful.
Here is the manual:
I didn't have this trouble with any of the other rigs because none of them required the use of negative numbers. My BITX 20 for example had an IF of 11 MHz and has the VFO running a bit above 3 MHz -- so the PLJ6 just adds the IF to the VFO signal and Bob is my uncle. Similar problem-free addition takes place with the other rigs.
I found some discussion on this problem on the internet. Here is one:
Some of the respondents didn't seem to understand the problem. Others hint that the ability to handle negative numbers was as some point in the code for the PLJ6 device, and may somehow be accessible, but no further info is provided.
I have already worked up a possible solution, but I'm interested in how you folks would approach this problem. Any thoughts or suggestions? I will reveal my solution in the days ahead.
What happens if you set the counter to add, and program it to add 2.4?
ReplyDeleteThat doesn't work. With a 12 MHz IF, to tune 7.2 MHz, you have the VFO at 4.8 MHz. 4.8 + 2.4 does equal 7.2. But look what happens when you tune to 7.3 MHz. You now need 4.7 MHz from the LO. But 4.7 + 2.4 = 7.1 MHz. So this doesn't work. But thanks.
DeleteYes. Just change the programmed IF frequency. The counter doesn’t care what it “really” is.
ReplyDeleteI thought the same thing and tried to find one that would correctly display frequency across the band. I couldn't find one. It is easy to find one that will properly display ONE frequency. But tune away and it all goes wobbly!
DeleteSounds like the programmer forgot to take the absolute value of the result....
ReplyDeleteThere are a lot of clones of this device, and there seems to be some variation in the programming. So other versions might not have this problem.
DeleteI came up with a solution: I re-purposed a little NE602 converter that I had built so that I could listen to 75 meter AM on my 31 meter Q-31 receiver. I retuned the input and output circuits and changed the crystal to 11 MHz. VFO from the Hodgepodge went into the converter, where it was shifted to around 6.3 MHz. I set the IF in the counter to around 1 MHz and put it in the add mode. Now the San Jian display plays well with the Hodgepodge. I will post a video on this. 73 Bill
ReplyDelete