Items for sale

 For sale  Comments Off
Feb 112014
 

Here are a few more photos of items currently listed on ebay.

OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA OLYMPUS DIGITAL CAMERA

 Posted by at 21:44
Oct 232013
 

Over the past few months I have had a steadily increasing pile of broken PICKIT3 PIC programmer / debuggers on my desk. Yesterday I found a few moments to fault find one.

I have seen the connectors fail before but this was different.

They all show the same symptoms, Target Device ID (0×0) does not match expect….

A quick comparison against a working one revealed problems with the programming voltage applied to MCLR. After further investigation I found Q6 a PNP SOT23 packaged MMBT3906 had failed. All I had to hand was a FMMT593 which works perfectly well.

All of the others had the same fault.

Now all that is left to do is work out why they break in the first place.

 Posted by at 19:24
Jun 152013
 

About 10 years ago I attempted to create a few High Dynamic Range (HDR) images. It was a time consuming process that involved manually aligning three or more images on different layers, then merging them into one. At that time I had access to an old copy of Photoshop at work. The technique sort of worked but took hours to complete and I was never really happy with the results.

Software and processing power has moved on in leaps and bounds since them. Today I use Paintshop Pro as my editing tool. It’s comparitively cheap and easy to use. Whilst browsing the help for something else I noticed that it had an HDR merge facility built in so decided to give it a try.

The source images were all taken hand held so alignment wasn’t perfect. Even so the tools in PSP have done remarkably well. I have to say that I find most of the presets to be not quite right, but they work as a starting point.

Experiments in HDR. Taken in Canary Wharf, London.

Experiments in HDR. Taken in Canary Wharf, London.

 Posted by at 20:17

The May UHF Contest 2013

 GD0EMG  Comments Off
Jun 102013
 

As usual Chris G0FDZ, Chris G4FJW, Dave G8ZZK, and myself joined Martin G4XUM, and Andy GD0TEP at Robert GD4GNH’s QTH. We’ve been taking part in this contest for many years. One day we’ll catch the dawn lift. That day wasn’t this year!

We didn’t work anything exceptional this year. The 3cms station wasn’t well so only a few QSO’s were made. Still, the Chineese, pub lunch, and curry were all good. Roberts breakfasts are always good.

GD0EMG 2013

The year when 3cms failed. Strangely, I didn't take any photos of the antenna systems this year.

 Posted by at 19:47
Jun 052013
 

My FT1000MP left my shack about a year ago and is now in service with another local amateur.  One of the issues that I had with it when I owned it was the purity of the transverter output. As I was asked about the issue again the other day, here is what I found.

I used the FT1000MP on 14MHz to drive my JavornikII 2m transverter, however the comments here apply equally if you are transverting from 28MHz.

The transverter output has some rather undesireable spurii either side of the main carrier. The offset from the main carrier varies as the VFO is tuned across the band so they cannot be filtered out. At worst they are only 45dB down on the main carrier. If you are running 400W into a decent antenna system these spurii are going to cause problems for other local stations.

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FT1000 Transverter o/p. 14.150 CW RF power control 12:00. Note spurs. RBW reduced for this shot.

Reducing the drive level cleans up the output and the spurii dissapear into the noise. This may not be an option in all cases as the transverter output level is already very low.

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FT1000 Transverter o/p. 14.150 CW RF power control 09:00. O/P level reduced by ~6dB. Note spurs dissapeared into the noise. RBW reduced for this shot.

The best option for me was to run the rig at about 25W into a power attenuator. This provided a cleaner signal at a level sufficiently high to drive my transverter. I am sure the IMD performance was worse though.

A long time after I moved over to a K3 I received a mail form a well known UK amateur who had spent some time looking into the problem. Unfortunately I don’t have his permission to post his email here but he pointed me at this article by Tom W8JI. If you have ever carried out a factory reset on your FT-1000MP the chances are that the IF TX gains are all set to default.

 

 Posted by at 17:32
Jun 022013
 

About a year ago I decided to update my website to make use of one of the free content management systems that are now available. Both Joomla and WordPress were duely installed and testsed. I read about the differences between Joomla! and WordPress and decided that Joomla was what I needed.

Having spent many evenings and lunch times playing with Joomla3!, and sucessfully using it to build a website for a local charity, Help a Maidstone Child, I have abandoned it for personal use and opted for WordPress. In the end it was the lack of a suitable comment system that put me off Joomla. There are free comment systems out there, I tried K2 and Komento, but I neither one functioned as I wanted it to.

So, here we are in WordPress. Given the current lack of new content on this website I am sure it will be more than adequate.

 Posted by at 21:00
May 222013
 

This is the first post in my 2013 photography project. It’s as much a learning exercise in using WordPress as it is about presenting the images. These images were taken at Spittalfields Market in April. I set out with the intention of capturing a series of images displaying vibrant colour. The market is well worth a visit, on the day we visited the Huguenots Festival was taking place so there were various cloth making demonstrations taking place.

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 Posted by at 22:16
May 192013
 

The FT847 is a great little radio but (in my opinion) has one major flaw. VOX is always on. If the radio is left in CW mode and you touch the key, it will transmit.

If you are running the rig in a system with a mast head preamp or a high power amplifier this can cause problems, and in many cases may cause damage.

The solution adopted by many FT847 owners is to pass both the microphone PTT and the key signals through an external relay. This is not entirely foolproof as the front panel MOX switch is still active. However, there is another, more elegant solution.

On the tuner interface socket there is a signal marked TX INH. Pulling this signal high prevents the radio from generating any RF. Keying the microphone, pushing the MOX, or touching the key will still put the radio into TX but no RF will be produced. Usefully the PTT lines from the STANDBY socket still work which make interfacing to an external sequencer even easier.

Below is the circuit that I use to allow the FT847 to be sequenced. It all fits neatly into the 8 pin connector shell.

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U1 is a 78L05 5V regulator. R1 is shown as 1K but can almost vertainly be higher, 10K will probably be fine. D1 is a schottky diode. The type is not critical, I used a BAS16 that I had to hand.

An alternative to this circuit would be to add a pull up resistor to the TX-INH line inside the radio but of course that means opening the radio.

Acknowledgements.

Thanks to PA4EME for suggesting using the TX INH signal.

Disclaimer.

This works on my FT847, and at least two others that I know of. It may not work on yours. I accept no responsibility whatsoever for any consequences of using the method described above.

73, Ian

Copyright G0AFH 2013.

http://www.g0afh.com

Dec 192011
 

My 2m station is in a good location on the North Downs in Kent. It is also line of sight to several broadcast transmitter masts which present a few problems for my receivers. Mast head preamps are a non starter for 2m.

Almost every receiver that I have ever owned has suffered from strong signal problems from the band 2 transmitter at Wrotham. If I connect a microwave power meter to the 2m array (2x17ele) I can measure several mW of power from the anttanna when it’s pointing at Wrotham.  Most of the RF is out of band, predominately between 88 and108MHz.

Here is a screen shot with the antenna connected to the anaylser. The antennae are pointing directly at Wrotham. To the right of centre is GB3VHF on 144.43MHz, slightly left of centre is a pager signal probably from the same mast at Fairseat. GB3VHF peaks at around -40dBm if I beam that way.

Below is a closer look at band 2.

For the past 8 years or so I have used a simple notch filter to deal with this. However, it’s performance isn’t that great and lets through more than I’d like.

This is the response of the notch filter. The blue trace is insertion loss, green trace is return loss. Peak attenuation is -31dB at ~93MHz. Insertion loss is around 0.5dB

Years ago I purchased a helical filter manufactured by Aerial Facilities Ltd. It’s beutifully made and has a much better response than the notch filter. It was originally on ~137MHz. I am still trying to tune out the lump slightly HF of the bandpass and improve the insertion loss.

 Posted by at 20:40

A new blog

 Uncategorized  Comments Off
Dec 172011
 

I have installed wordpress to allow more frequent updates to the G0AFH site. Updates currently happen about once every 3 years so don’t expect much any time soon.