Monday, April 30, 2012

Ground Radial Plates

I’ve decided to change my ground radials on the 30 meter vertical. I’m limited in how many radials I can lay out with the current box setup and through checking via the MFJ I am still getting 40 ohms at reactance (even with all this wet weather), and really I'm looking for the standard 36 ohms and I'm certain it's down to the number of radials I currently have laid out. So I am going to make a simple ground radial plate with a minimum of 60 connections hopefully more if I can fit them in.
What’s fascinating is the different types of plates you can find on the market and the prices. Basically all I’m looking for is a good piece of plate aluminium which I can cut to size, add a connector for the coax and drill as many holes as I can around the edge. Looking on Ebay last night I managed to pick up a fairly chunky plate for £2.00 which I’m now waiting to arrive.  Some plates I’ve seen on the internet can cost as much as £40.... crazy!
Here’s a few examples that I particularly like and may have ago at copying.

This home brew plate looks fairly simple with the antenna connector coming up through the middle but it looks as if its limited with connector numbers, to get round this and similar to my box there is more than one wire connected to each bolt.

Here's the DX Engineering favourite which I might well use to copy but put the coax connector plate on the edge instead of the middle. It's a nice big chunky plate that will probably last for years.

Home brew "Tiny plate", looks like an old sink drain! But hell as long as it works.

This is from a UK company called Antenna Engineering, I like the way the coax connector is bolted on to the plate and a good strong simple ground spike too. The company does some great antennas and is well worth a look.

And here's my present box, it works fine but you can see I'm limited on the amount of radials I can insert (20 but I can double up) and although it's an ideal light weight box for portable work it really could be much better now I've got it permanently set up in the garden.

QSO's in Stormy Weather

With gales forecast for this weekend I brought the cobweb right down to a safer level (about 12 ft) and I was right to do so as the wind picked up Sunday morning and we had gusts up to 60mph.
The W3DZZ was being blown all over the place and three times I ventured out in the wind and rain to do running repairs where the wire had broken free from one of the traps, a well-known problem with the W3DZZ, those traps are a real pain to fix in place! In the end I gave up, 40 meters was busy anyway with a big contest going on and operators were not going to be bothered with me moaning about my antenna problems.
It’s still surprises me when antennas are limited in height how they can still work, especially the cobweb which although only 12ft up still managed to work most of Europe and I could even hear the VKs but of course there was no way they could hear me.
At one stage the 30 meter vertical was bending virtually at right angles but easily proved to be the best antenna during the storm and I was happily qso ing with most of Europe telling them how bad it was, while most of them were giving me reports of fine warm weather!
It was a classic European weather pattern with the jet stream sailing right up over the English Channel bringing stormy weather to the north and much milder warmer air to the south, while Britain was being battered by storms much of Europe was having above average temperatures!

Monday, April 23, 2012

Log Book Review and Inrad Filters

Yesterday morning I managed a quick qso with a Cuban station, a first for me for some time, I think the last Cuban station I contacted was round about the last sunspot maximum.
Looking at my log book I think I’ve done pretty well considering everyone is saying that this sunspot cycle has not been so good. Along with the usual Europeans and of course across the pond I have VKs, ZLs, JAs, and a few Chinese and Vietnamese not forgetting my couple of stations from Antarctica.
This is the first peak that I used all homebrew antennas so I’m really pleased and amazed that everything has worked so well. I’m sure if I had a nice big yagi the list would be much more impressive, but I’m certainly not complaining.
I’d love to get some Indian stations but for some reason so far I've missed out, probably I suspect just from timing, but there is still plenty of time and hopefully the peak will continue well in to the year.
I’m still awaiting my Inrad filters for the mark V, I thought they would have arrived by now but on ringing up the supplier it seemed there had been a mistake in my order so it’s going to take another 2 weeks.
Incidentally whilst inquiring on the phone I bit the bullet and also ordered the IF improvement MOD, a friend of mine has it installed on his Mark V and was telling me how good it is in reducing the background hiss.  It’s now very noticeable how sometimes when coming across a station where it’s crowded I think I could really use those filters!
I still haven’t had the time to drop the cobweb down for its yearly service, when I do get round to it I shall post some pictures.
I’ve decided to try and find myself a cheap 2m rig; I used to have an old Yaesu FT 480 that I used when learning CW many moons ago, but once qualified I sold it on as I found it wasn’t getting used very much. Since the moxon has been taken down I now have the light weight rotator sitting in the shed doing nothing, so it would be quite nice to build a small 2m yagi and see what DX I could get.

Wednesday, April 11, 2012

General Update

I think I may have gone over the top with ground radials, but from what I gather there is never enough! Clearing out one of the sheds the other day I found some old chicken wire and realised it would be another excellent ground radial for the 30 meter vertical and so took it round the back of the garden unrolled it and connected up. I checked the swr and it’s still at 1:4 but the resistance is now a healthy 38 ohms. It’s very noticeable however when there has been a good downpour the antenna behaves so much better, and the resistance drops to around 36 (the perfect score) obviously damp ground plays such a huge part with vertical antennas.
It seems that the bands have been fairly quiet recently, certainly when having a quick listen 10 and 12 meters have not been as good as the previous month. Although unfortunately through work commitments I have had little time to concentrate on playing with the radio.
I still have not had the chance to service the cobweb, but in the meantime managed to purchase some more speaker cable (42strands as per the original instructions) so that should the need arise I have plenty of spare available. When I do actually get round to the service I will take some pictures so as you can see the build, (I never did post picture when building the antenna).
 Further tests on the FL2000b amplifier have shown that everything is running well and the amp is far more stable, no doubt from replacing the damaged resistor within the parallel choke. I've now had it up and running to 300 watts on all the bands and so far good reports have been recieved which is excellent news.
I've been getting itchy feet again within the antenna department and I’d really like to have a go at building some kind of antenna for 160 but have the usual problem of not enough room. To do this I would have to replace one of the existing antennas otherwise the garden would begin to look like a mess and certain family members could well complain! The obvious choice is the W3DZZ, which is currently covering 80 and 40 meters, I will look in to seeing if I can add another trap for 160. Further updates to follow.

Wednesday, April 4, 2012

Yaesu FL2000B Update

Good news I have managed to fix the FL2000B! A bit of soldering and a good clean out and fingers crossed so far the amp is working well. I've only loaded it up on 15 meters but it is much more stable than before so hopefully after further tests all should be back to normal.

The cause of the problem is still unknown but I suspect I didn't have the High Voltage cage correctly seated which caused the main fuse and the resistor on the safety interlock switch to blow.

However the two resistors on the parasitic choke from one of the tubes had burnt out and that would not be caused by the first issue so something else was certainly not right. I ordered some new resistors and carefully replaced the damaged items but replacing the two resistors on the choke with just one, (no idea why there had been two in the first place, maybe the previous owner could not find the right value), followed by a good clean out and then lubricating all the switches. This is the first time I've delved in to the old amplifier and everything was a bit unknown, but I must thank the guys at and my local club CARA who gave advice and help which was extremely useful in the fault finding.

The repaired parasitic resistor all soldered up and ready to be refitted.

Just as important I have learn't a lot about the old valve amplifiers and saved myself a ton of money which can only be a good thing!
More testing to follow so I shall keep you updated.

Sunday, April 1, 2012

The Trials and Tribulations of a Yaesu FL2000B

Having owned my FL2000B for around 8 years and used it on rare occasions but more so when I had the FT990 to get a bit of power out when needed, I decide it was time to give it its monthly warm up and also give it a good clean as it was pretty dusty inside the cabinet. 

Once unplugged and after removing the top cover I decided to delve deeper and check out the tubes. So I removed the PA cage and released the safety interlock switch and proceeded to clean. All complete I put everything back together making sure the safety interlock was back in place. I turned on the amp and let it warm up and then there was a loud bang…………..Oops something was not right!! 

Well of course I inspected fearing the worse that the tubes and everything else had blown up. Further investigation showed the main fuse had blown and that the parallel parasitic choke containing two resistors over one of the 572B valves were both burnt and also a resistor on the safety interlock switch had also gone. 

The burnt out resistor on the safety interlock switch

Thankfully from correspondence with fellow hams from my local club and on agreed that it was unlikely I had damaged the tubes. So the first thing to do is order some new resistors which I have done for the parasitic choke but am still trying to find out what the value is of the resistor on the safety interlock switch is. Of course I may well have damaged other parts but there is nothing visible to see and only further testing once I have the new resistors will show anything further.

 One tube removed and the offending parallel resistors and safety lock removed

Further updates will follow as I continue with the repair, I have to admit although I was devastated when it went bang, I'm actually quite in to fixing it as I'm learning loads about old valve equipment!