I thought my audio level had suddenly gone bad the other day. Turned out I had plugged in a webcam and Windows 7 decided that it should be the default audio input device. Changed the default back to rear-panel microphone and all was well.

I appreciate you taking the time to reply James, but I doubt those groups will be able to help. I need to find a Robot 1200C owner from the 1990s who used the HiRes program before PC-based SSTV systems took over.

73, Paul G4IJE.

A friend of mine still uses a Robot 1200C for SSTV and until recently ran the "HiRes" program by N9AMR to transfer pictures to and from his old DOS PC. Unfortunately his hard drive has just failed and I've tried my best to recover the program but it wont run, possibly due to its copy protection. We have the original program disk (3.5" floppy) but it only allows one installation; you have to "uninstall" the program back to the floppy if you want to reinstall it, and without a working version we cannot do the uninstall. I believe the author is now a silent key so that route is lost to us. Does anyone have a copy of the program they no longer use? It's all pretty ancient but my friend would dearly like to get it working again. Thanks.

BTW, I think the version of the program is 2.1 which I think was the last version for the Robot 1200C. It installs in a directory called "HIRES21".

Does anyone know if Tom Jenkins, N9AMR, is contactable via email? I tried n9amr@sbcglobal.net which is given on qrz.com but the email bounced. I have just one small query relating to the Robot 1200C scan converter and his "HiRes" program that he may be able to answer for me.

Many thanks,

Paul.

Does anyone know if it's possible to interface a modern PC with a Robot 1200c and run the old "HiRes" program (written by Tom Jenkins)? The program is DOS and the interface with the Robot is via a parallel printer port. I guess even a modern quad-core PC can be made "dual boot" (though I haven't done it for years!) to give a DOS option but I have serious reservations about getting it to talk to the Robot. I guess a PC with a "proper" parallel port on the motherboard (rather than an add-on card which might not work outside Windows) would be the best chance. A friend of mine wants to replace his 15-year-old 486 DOS PC with a modern one so he can get on the Internet, but would love to run his old SSTV system on it as well. Quite a challenge I suspect!

Thanks for your help.
 

Interesting article. My 3 element quad design shows more gain than my 3 element yagi design but I don't have the exact figures to hand. I usually model (with EZNEC) using real ground and real height above ground so I should be seeing something fairly close to reality. I will check my models tonight.

I would like to build a 3 element quad for 6 metres and I am considering options for the spreaders. I can buy fibreglass rod online (the sort of stuff that is used for kite building) but I have no idea what diameter would give the required strength/rigidity for a quad spreader. For 50 MHz, the total diagonal for a spreader is a little over 7 feet and obviously this will be fixed to the boom at it's centre. So, assuming fairly lightweight wire for the actual quad element (say #14 or #16), what diameter fibreglass rod would do the job? If had a local store where I could get my hands on some rod I could quickly get a feel for the right thickness by just "whipping" it about a bit, but I don't have anywhere nearby. I'm thinking maybe 4 or 5mm would be sufficient. What do you think? Perhaps I should add that I'm that looking for a fairly lightweight antenna that will last for a year or two; I don't need something that will last for years and stand up to hurricanes and other extreme weather.

Very occasionally my FT-450 suffers some kind of lock-up on receive. This evening I was listening on 6 metres (the only band the rig is used on). I reached for the dial and tuned a few KHz up the band; all receiver noise ceased suddenly and the s-meter showed a constant S3. The receiver was not completely silent - there were a few low-level clicks audible and there were low-level clicks as I tuned the dial up and down. I have heard of rare VCO problems on the FT-450 with a "FAIL" message on the display but my display was completely normal. Band and mode switching seemed to work as normal with the usual relays clicking in all the right places. The radio would go into TX when the PTT was pressed, but I didn't apply modulation in case something was harmed with the rig in this strange condition. All front panel buttons responded normally but the receiver remained silent (apart from those faint clicks) at all settings. Naturally I checked the squelch and RF gain setttings ;-)

As before when this has happened, the fix was easy: I switched off and then on again. Normal operation resumed immediately.

This has only happened about 4 times in 3 months, so it's not a major problem as long as it doesn't get worse. The rig is under warranty but I am loathe to send it away for service as it could be very difficult to trace such an elusive fault. Has anyone heard about/come across this problem with the FT-450?

I like the sound of VA7CPC's methodical approach. The other thing to check for is RF feedback. Is your audio quality good without the processor? Next time someone give you a 59+ report at your usual power level, turn the power down by 10dB (you should still be strong enough) and ask them if your audio quality improves. If it does, you may have a low level of RF feedback.

Actually my FT-8900R was supplied with the MH-48. There was a time when we didn't get many DTMF mics in the UK since we have never had "phone patch" facilities. Nowadays with so much internet-linking of repeaters, everyone wants a DTMF mic and they are much more common.

Anyway, that's mostly irrelvant as I was simply using the MH-42 schematic as an example of a simple ptt/up/down circuit that would work with the FT-8900R. I guess I'll haul the rig out of the car this weekend and give it a try.


73, Paul G4IJE.

Has anyone built their own microphone (hands-free mobile mic perhaps) for the Yaesu FT-7800, 8800 or 8900? Did you include the up/down buttons? I'm having trouble finding definitive wiring information. Best I can come up with is a schematic for the MH-42 microphone, which is an option on these radios. It looks like PTT, UP and DOWN functions can all be done on pin 6 by wiring three resistors in series. If you ground pin 6 via 27k you get PTT, ground it via 27K and 39K in series and you get "down" or ground it via 27K, 39K and 82K in series and you get "up". Obviously one would set the microphone type to MH-42 in the radio's menu. Can anyone confirm that this is correct?

Thanks and 73, Paul G4IJE.

There's a good hairpin calculator in the HAMCALC suite of software by VE3ERP. I've used it a couple of times and it was spot on. Google HAMCALC for the download site.

73, Paul G4IJE.

Amazing the myths you pick up over the years. I'd always believed the 40 stood for "40 days", the time it was supposed to last before needing to be re-applied. Guess that one is bunkum...

You can forget the F layer for the next few years but the Sporadic E season will be getting underway soon. It's there every summer (roughly May-August) and doesn't rely on sunspots. Have fun!

Look out for a TS-130 which is almost identical but has the WARC bands.