Archive for the ‘Uncategorized’ Category
A different route to work – different things to listen to
June 23rd, 2010 | 
Author: I took a different route to the station this morning. Leaving home a little bit earlier than normal, I popped into Oxford to see our friends at Jack FM. It’s lovely to see them and see how effortless they make producing a great show appear.
As I was driving down the A34 from Oxford to Didcot, I popped the FT8900 on and had a listen around. To my surprise the GB3CF repeater at Charnwood Forest in Leicestershire was coming in very strongly – approaching S8 on some of the hills to the south of Oxford..
What was interesting to me was that my route this morning wasn’t more than 10 miles or so from my usual one – but it’s quite unusual to hear GB3CF on the normal route – certainly at that sort of signal strength.
New DVAP firmware available – fixing TX problems
An e-mail from Robin, AA4RC to the DVAP Dongle Yahoo group today announces the arrival of the latest release of firmware (v1.05) for the DVAP. Robin notes that he hopes that this should resolve the transmit issue that some people (including me!) have been having. Moe, AE4JY is credited with finding and resolving the problem. Thanks Moe!
The revised firmware may be downloaded from the Downloads section at http://www.dvapdongle.com
More on the Minimalist Transceiver
'The Bay' minimalist transceiver (without component values)
Back in March I wrote about my experiments with a minimalist transceiver design that was published in Sprat earlier this year. Today I received an e-mail from Claude, W5FYI, who enquired about this work. He wrote:
I, too, am interested in building G0EBP’s FET transceiver. One thing that puzzles me is reference in the Sprat article to the 560pF C5. Tony says it is for the final filter. Is he referring to the FET’s capacitance, or his value for the pi filter’s capacitors.
When you get your schematic ready, please let me know.
I thought I would share my reply as others may be interested:
Thanks for the e-mail.
Yes I wondered about that reference to C5 too. I presumed it was the 100nF cap connected to the drain and the inductor on one side and the filter on the other.
I have done quite a few mods to this circuit and still tinkering trying to get a 700Hz freq. offset on transmit, so avoiding issues if someone is zero beat. My first attempts were poor, using an idea in Solid State Design for the Radio Amateur, which plays with some feedback in the oscillator circuit (Fig 6 p36 if you have that book). I see a brief freq. shift and then it seems from my freq. counter the oscillator locks back again. Perhaps I need to switch in the capacitance with the crystal which I think will work better. Been too busy recently with work to finish this experimentation.
Back to my main changes that I did.
1. I changed the oscillator to a FET based Colpitts with a J310. Better waveform, but lower output than a 2n2222 and hence only about 1/4W out with 9V.
2. I have used a different muting process. On keydown I put +Vsupply to pin 7 of the LM386. That mutes the audio op-amp. See LA3ZA, Sverre’s notes on this at http://www.qslnet.de/member/la3za/Pixie_mute.htm
3. Rather than have the key in line with the supply I included another transistor (PNP BJT) so key is connected to ground for transmit. This helps if you mount an un-isolated socket for the key jack in a metal chassis.I need to finish off the experimenting with the offset and then write up the changes for SPRAT.
I looked in my notes and see I blocked out the basic circuit but have not added any component values, so I attach it here, to help you. The offset circuitry is not included. I think you will be able to work out the component values from the original diagram. If you need the calculated values for the Colpitt’s oscillator, let me know and I can supply those.
Hope the above helps you.
By the way I have started to call this transceiver “The Bay” after Morecambe Bay where G0EBP lives and coincidentally where I was born and grew-up.
The draft circuit diagram is above. It is unfinished but still gives a good idea of what I have done with Tony’s, G0EBP circuit.
When I get time to return to this circuit I will report findings and updates here on the blog.
Now I’ve got too much to write about
It’s been quite a while since I wrote last, mostly because I didn’t have all that much that I felt was interesting. There were a few bits here and there, but none worth writing about. All of a sudden, I have a lot to write about.
I’ll start with a couple of relatively quick things here, and try to get another update out in a couple of days with more.
First, I may be on the air at some point next Wednesday, Thursday and/or Friday as K2DBK/VP9 from Bermuda. I’m going to be there on vacation and while I hadn’t planned on getting on the air, through a series of events I wound up connecting with Ed, VP9GE. If you’ve worked VP9 on 6m, chances are that you’ve worked Ed. This was all very last minute, but I’m trying to arrange at least an “eyeball QSO” (that’s a face-to-face meeting for any non-hams out there) with Ed while I’m in town, and Ed’s already said that he’s going to try to get me a license to operate from there. I don’t know how much I’ll know before leaving, but hopefully if I make it on the air I’ll get spotted on the packet clusters, and if possible I’ll try to post here, on my page at qrz.com, and even on twitter.com (@k2dbk).
The other quick thing that I wanted to post about was that fellow blogger Jeff, KE9V, has started a new podcast called “Cornbread Road”. As Jeff describes it, it’s a “different kind of podcast”, and here’s what his “About” page says:
Deep in the Heartland a small group of ham radio enthusiasts enjoy an idyllic existence of wide open spaces, no antenna restrictions, low-noise levels, dark skies, and good fellowship. But things aren’t exactly as they seem on Cornbread Road. Unexplained lights in the night skies, satellite signals masked from the ether, strange late night visitors to this small farming community…
Cornbread Road is a ham radio mystery delivered in tiny audio giblets.
I listened to the first episode during my ride into work this morning and I really enjoyed it.
AES 10, SGC -2
After using the tuner for about year, one camping trip it stopped tuning altogether. I popped it open and the PIC chip was hot and the tuner was down for the count. In disgust I tossed the SG-211 in a closet for a year and forgot about it. I decided to give the tuner another chance and sent it to SGC to have it repaired for the flat $55 rate. Reading online reviews, I figured the unit might tune better with new firmware which was probably updated since this unit was manufactured. I got the SG-211 back about two months later; the tech said the PIC was bad and they ended up replacing the whole circuit board with a reworked board. Upon getting it back I tested it with the FT-817 and it couldn't find a match on any band with any antenna. The "reworked" board was a mess. You could tell someone spent a lot of time messing with this board when they were repairing it; it looked like it had been through a war. There were cold solder joints on the antenna terminals and on many of the matching network capacitors. I sent the unit back to SGC again and in a few more weeks it was repaired. The tech said a relay was burnt, probably from high power. I never had the unit connected to anything other than the FT-817 which runs only five watts. I got the unit back and it worked, though it still can't tune its way out of paper bag when connected to a 50 ohm load and it takes forever to find a match on several bands.
Fast forward a year later. I'm looking for a remote antenna tuner for a 100 watt setup so I can get rid of open ladder line coming into the shack. I had been working on a homebrew remote balanced antenna tuner for some time, but it's obvious I'm not going to complete the project in the next decade, so I'm just going to break down and buy a commercial unit. I look at Icom's remote tuner and it looks like you have to mate this with an Icom rig, so I shy away from it. MFJ offers a unit, though from the reviews it sounds like one of their indoor autotuners thrown into an outdoor box. I like MFJ to an extent, but you just never know what the solder job is going to look like inside any of their products and I don't want to risk it with an outdoor unit. SGC offers the SG-237 which is in a nice package and gets good reviews. After my experience with the SG-211, I'm not sure why I did it, but I went ahead and bought one. Call me stupid, but I thought I would give a "Made in America" company a second chance. The unit arrived and I hooked it up to my 60m dipole fed with ladder line. It tunes most of the bands fairly well, but on 80 meters it can't find a match anywhere. Grumble. I mounted the tuner outside in an enclosure as its permanent home and shortened the ladder line. Then it would match on the lower end of 80m, but it was still befuddled with the middle and high end. I futzed around adding sections of ladder line and after several iterations it would begrudgingly match the entire band though it would often need coaxing from the bottom of the band up through to get a match on the top end. So it worked "good enough".
Fast forward a week later. I had been on a business trip for a week, and I came back and connect up the power to the remote tuner. I key up on several bands and I can tell the remote tuner isn't trying to match at all. Grumble. I go outside to troubleshoot it. Everything is connected correctly and the unit is getting power. I disassembled the outdoor setup, brought it inside, connected it up on the bench and it indeed won't tune at all. I popped the tuner open and it's definitely sensing RF but it doesn't sense any SWR, so it thinks everything is hunky-dorey, no need to tune. No burn marks and nothing popped inside, so I've got a doorstop that lights an LED.
I contacted SGC over email and spent several days troubleshooting the unit. After getting to the limit of what we could do over email they said to return it for repair or talk with AES where I bought it and see if they would exchange it. Having experienced SGC's glacial repair speeds before, I called up AES and spoke to the service department. The guy there didn't even ask for any details like my account or order number, he said just box it up, send it in and they'll get a new one out to me. I did just that and AES shipped a new unit rather quickly.
The new SGC unit works, but I'm afraid to do much with it. After such a bad experience with two different models, this unit is likely going to be used only for Field Day and other select outings, and I'll always have a backup manual tuner around. I certainly won't put it into permanent use.
I have to give kudos to AES for their outstanding service over the years. I've never been disappointed with them.
DVAP fun and games
As you might recall, I upgraded the firmware on the DVAP the other week. I hadn’t used it much since the upgrade. This evening I thought I’d play a little D-STAR. I found that I would start transmitting and then I would lose connection and my audio would be lost. One or two other people have been experiencing the same thing. Indeed, Ron, KA2HZO that I was speaking to this evening was having exactly the same issue.
Ron downgraded his DVAP firmware back to 1.01 and found that performance improved. I’ve done the same and things seem better. I had experienced the problem from time to time myself on 1.01 but it seems less frequent.
Of course, it could just be an issue with the internet connection – something else on the PC which the newer version is slightly less tolerant of. I’m sure it will be resolved in due course. But for now, I’ve downgraded to the v1.01 of the DVAP firmware.
Update: 21st June Had an e-mail last night from Nidge, G0WFS. He’d experienced the same problems as me with his DVAP running under v1.04 of the firmware. He reverted back to v1.01 and all is well again. So it looks like there are some issues with v1.04. That doesn’t mean it won’t work for you, but if you do have problems, a simple reversion to the v1.01 firmware should have you back up and running reliably in an instant.
An interesting Es day
There’s been plenty of VHF Es buzzing around here today. It started off, literally with a buzz on 50MHz as I was driving down to the Post Office in the next village this morning. I heard some TV buzz on 50MHz, almost certainly out of Eastern Europe. A few stations started coming through including YU1EXY, the Belgrade University club station.
After that, I had plenty of things to do and didn’t get to the rig again until around 1530z. There seemed to be a contest going on 50MHz. I worked LZ9W (KN12) and YT2F(KN03) as well as an EA6.
There were some reports of 144MHz Es too. At one stage, I could hear DLs working Es that I couldn’t hear any trace of. At 1735 though, I heard LZ2ZY (KN10) briefly. He was working into Belgium at the time and I didn’t hear him work any Gs. G4MKF, not too far from me, worked a station that I couldn’t hear at all, but the opening seemed pretty fleeting. Though it was a shame not to work LZ2ZY, it was great to hear him!
