Both Cobwebs Now Up and Running

Well after much playing about with tuning and trimming, I finally got the G3TPW Cobweb back up on the mast yesterday evening.

After my initial tuning the other day I had to dismantle the antenna as the weather was proving very bad, so yesterday by the time I had re-assembled and started up the tuning process the morning had passed quickly by. Finally with a bit more trimming completed, I climbed the ladder with antenna in hand and clamped it in to place.

I switched on the MFJ 259 and did some checks, the SWR was all over the place, I had a problem, something was definitely not right and after a quick check of all the coax cables, I had to make the decision to bring the antenna back down, and so I clambered back up the ladder and removed the antenna.

I spent most of the afternoon with the terminal box open trying to figure out what the problem was, I knew it was shorting somewhere but in the end I had to go through each connection to find the short. Eventually I found the problem, it turned out to be one of the 12 meter elements had split at the join to the choc block causing one of the U connections to short and all it needed was re-stripping. Then it was just a case of re waterproofing the box, sealing up and mounting back on the mast.

Dusk was fast approaching when I clambered back up the ladder and attached the cobweb back on the mast, I quickly said a prayer and did my checks on the MFJ and thankfully all proved OK. 

Finally back on the mast!

The SWR measurements are now pretty good, they are all set for CW except for 10 meters which I set for 28.500 as I like an occasional rag chew on 10.

14.000 - 1:4

18.070 - 1:0

21.050 - 1:0

24890 - 1:2

28.500 - 1:1

With the G3TXQ cobweb now set up in the attic I am at last ready to do a bit of testing with both cobwebs. Obviously as this antenna is in an enclosed space there is bound to be a difference. The most noticeable being the background noise but that cannot be helped as the attic naturally has bricks and mortar and electrical wiring.

Here is the final SWR reading for the G3TXQ:

14.075 1:5

18.080 1:4

21.073 1:3

24.890 1:1                        

28.015 1:1    

As suspected there is not a lot of difference, but the SWR is slightly higher on the G3TXQ on a couple of bands (most likely because of the attic positioning). I could trim to match the frequency of the G3TPW, but to be honest I couldn't be bothered to get it exactly the same. 

Physically the G3TXQ is far lighter and easier to handle also the tuning is much quicker because you only have one wire for each element. But that said, I do like my G3TPW, it is heavier and chunkier with my larger home made plates and it definitely feels more solid especially with the windy condition we have round here.

It was very apparent when lifting back on to the mast how much heavier it was compared to the G3TXQ, you feel the lighter cobweb would literally blow away in the wind, although that said it's exactly the same build just lighter materials.

The main difference on receiving is of course the background noise but if the G3TXQ was raised outside on my mast I doubt you would know the difference when listening. On transmit I've now used both cobwebs on 20 meters and reports from both are good with the G3TPW showing  slightly stronger RSTs, again no doubt due to due location.

So all in all as suspected there is very little difference, for me I'd go for the G3TPW simply because it feels stronger, but that personal choice from QTH circumstances. It's been fun servicing the old cobweb and building a new one and I hope you have enjoyed the entertainment as I've struggled along. I'm not a technical antenna geek so all this is very basic but hopefully gives you a rough guide to both types of the antenna.

I'll probably remove most of the posts I have regarding the Cobweb antenna and place them on a separate page so that potential builders have all the information together.

I'm not sure what I'm going to do with the G3TXQ cobweb now, so for the moment it's sitting snugly up in the attic out the way. Currently I'm saving up for either a K2 or a TS590 so I'm tempted to keep the G3TXQ and connect to the new radio, then I'll be spoilt for choice with two cobwebs!

PYE Radio Restoration

Whilst up in the attic rummaging around for Christmas decorations I came across an old radio/gramophone that had been sitting up there for the past 10 years, before that it had been sitting in the cellar of our previous house, totally unloved! It belonged to my XYL’s father and had been purchased many years ago.

I brought it out of the attic and gave it a good check over; blowing off the dust the on off switch had a small crack and the center cover on the left control was missing, the wooden cabinet was sound but had varnish peeling off, otherwise everything seemed to be there. On the back was inscribed “PYE R32” so I did a bit of investigating on the web. 

The original web photo

 It seemed the PYE R32 was built in the 1960s and could be bought for the vast sum of 28 guineas a lot of money in those days. It looked like an old valve radio but in fact was a transistor based rig, presumably, transistors were still in their early stages so the R32 was made to look like the reliable valve system. Removing the back cover everything was covered in a thick dust, it was then that the radio instinct took over and I knew I had to get it working! 

I gave the insides a good clean, first with a vacuum cleaner using a small spout and brush and then with small tips of cotton wool buds dipped in electrical cleaning solvent. Gradually the dust came off and it was almost as if the PYE was slowly coming back to life as each layer of dust was removed. 

 Once I felt everything inside was relatively clean I decided to connect a battery and see what would happen. Bingo, it came to life, I tested both the MW and LW ranging up and down each band and all seemed OK, the volume was a bit scratchy but some solvent on the pot soon cured that. The tone worked well and interestingly it had its own little antenna system that could be rotated within the cabinet which was rather neat and worked really well, bringing in European stations when you turned the antenna. 

 So now I knew it worked it only seemed right and fair to restore the cabinet back to its original condition. I decided to tackle the top first as it was definitely the worst effected, I gave it a good coat of paint/vanish stripper and then gently peeled off the remnants, finally I finished off with some serious scrubbing using wire wool. 

Leaving it to dry off for 24hrs I then sanded down the top, cleaned it all up and applied some varnish. Whilst I write this post it’s still drying off but if all is well I will then attack the front and both sides and re-varnish the whole cabinet.

I must admit just with the top done it looks better than the original picture I took off the web, should look brilliant once I've completed the sides, more pictures to follow once it’s all completed.

A 1:1 Balun

Whilst the cobweb is being dismantled and serviced I've put up a 20 meter inverted V dipole, just so I can use the OHR100A which is set for 20M. The dipole is completed with a 1:1 Balun.  

The ugly balun is very simple to build and does the job of removing any stray rf off the outside of the coax and away from the shack. 
It only took me a morning to make and it's from various bits and pieces I had lying around, an odd length of guttering pipe, some spare coax with an SO239 attached at the bottom of the pipe. The two wires from the dipole attach directly at the top of the balun via a choc block.

It's a bit rough and ready but as long as it does the job I'm not too bothered as it will be up 30ft and no one is going to look at the cosmetics!

The cobweb has as previously mentioned been dismantled and is now lying in the shed with the connection box drying off. Once its dry I will add some more silicone and drill some draining holes in the bottom of the box. 

The replacement fibre glass poles arrived but on closer inspection were just too thin to be used to hold the twin speaker cable, so I've found another supplier and re-ordered. 

The wooden poles are actually in not too bad a condition but I would prefer fibre glass to add strength and to make the antenna lighter. The new poles must be near to an inch in width to fit the metal sleeves and will be hollow therefore lighter.

Servicing the Cobweb Antenna

Finally I've got round to begin the service of the home-brew Cobweb. Taking it down from the mast wasn’t as bad as I thought, I decided to do it now as the weather forecast is not good with high winds expected over the next few days, so while there was a break in the weather I zipped up the ladder and began the removal process.

 Once down the initial inspection was that it didn’t look too bad considering it’s been up on the mast for nearly two years and been subject to some pretty bad weather conditions. A bit of rust here and there on the metal tubes that hold the wooden poles, but perhaps through luck or my building capabilities it has managed to withstand all that has been thrown at it! 

  The wooden poles and the box are covered in mildew and slightly bowed, but still sound, the cables are fairly loose which I suspect is the main reason my SWR has been out, especially on 20 meters which at the last reading was 2.5. Interestingly I thought the box would have been pretty rusty inside but surprisingly looks very clean apart from a good ½ “ of water slopping inside, first thought was hmm, I forgot to drill any draining plugs!

 The wooden poles are going to be replaced with fibreglass, I managed to find some ex army surplus which should do the job nicely but I will have to wait as I’ve only just ordered them so it will take a few days to arrive. Since the main box is in such good condition I will do little except give the outside a good scrub and more importantly drill a couple of draining holes. 

The silicon grease has done its job and kept the contacts all clean and rust free, I'm amazed there is no rust on the copper wire or the steel screws. Originally I bought a Cobweb (back in the 90s) for the grand sum of £160 and when I sold it I remember inspecting the box and seeing how badly rusted everything was, so I was expecting the home-brew to be the same, just goes to show what a bit of silicone will do to protect.

Over the next few days I will tighten the cables and recheck the SWR and if needs be replace any that are suspect, luckily I have some spare cable that I got last summer from Maplins, (our version of Radio Shack). 

Looking inside the box it is a remarkable simple system that is very easy to build and yet gives great results. This is easily the best antenna I've ever built and quite honestly if I can build one anyone can. If you want further information look at the Cobweb Revealed website or alternatively please ask and I'll be happy to help where I can (but I warn you now I don't understand the theory, hi hi). I will include as many picture as I can during the service process so you can see just how easy it is put together.

OHR100A Completed

The OHR100 A is now complete, a few QSO's later and I must admit I'm pretty impressed with this little QRP radio especially on the receive side. The Bandwidth takes a little bit of tweaking to get it just right but works well and can quite easily cut out the clutter from other nearby stations. So far I've had some good reports with stations around Europe and I have no doubt that I'll be able to contact across the pond with my 7 watts of power.

I've managed to get hold of a frequency counter off Ebay which has made a big difference, I don't have to guess where I am within the CW side of 20 meters which does speed things up a bit when searching for QRP stations. 

Inputting the IF offset frequency took a bit of thinking as I'd never done it before, but after reading and re-reading the instructions I eventually got there and had it all set up. The casing is a bit scruffy, but I'll give it a lick of black paint or some Hammerite to tidy it up a bit. I fitted an internal 9v battery and also added a small on off switch to save power when not required. It does the job nicely and I amazed how quickly I built it all up, another thing 6 months ago that I wouldn't have had a clue at doing!

I eventually gave up on the old TH-215 E and went shopping on Ebay, I managed to pick up a TH-22E for a few quid. It's an excellent little radio and works well when connected up to the Yagi, only 5 watts but that's all I really need as I'm 750 ft above sea level so can get out pretty well on low power.

The next project I must get round to (having said I was going to do it back in the Summer) is to take down the Cobweb and give it a good service. The SWR on 20 meters is up at 2.5 so I'm having to use the ATU all the time now for the RMs and the OHR. It probably just needs tightening, but I'm going to open the box and give it a good clean and re-grease the connections, after all it has been up there for a long time now. I'll take some pictures so you can see just how easy it is to build one!

I've got 10 days off over the Christmas break so I shall pick a good day weather wise and do the work! Also over the break I am going t have a good think about what to do next radio wise, another kit perhaps, or maybe an old transceiver that needs a bit of TLC? Well see what happens in 2013.

On that note May I wish you all a Merry Christmas and a Happy New Year.

OHR100A Build Part 2 (The Chassis and Alignment)

After re-checking all the soldering and making sure there were no obvious mistakes, I started on the chassis, firstly installing the SO239 socket and then attaching the optional ten turn VFO tuning pot followed by the AF and RF gain switches and the Bandwidth and RIT switches. The wiring instructions were fairly easy and I soon had everything connected up and ready for a smoke test. 

 All ready for the smoke test

The only problem was I didn't have a 13.8v power supply! The RockMites run off batteries and the FT1000 MP V has its own separate power supply. So on to Ebay and I quickly found an old but unused power supply for the princely sum of £15.

Two days later (a miracle in postal terms) the PSU arrived and after wiring in a 1A fuse I was able to carry out a smoke test. Do you ever have that feeling of dread, fingers on the switch wondering if you really will get smoke or just nothing happens? I must have been waiting for half a minute before I pulled up enough courage to switch the transceiver on. I turned the switch and bingo, the radio came to life ....what a relief!

Once I'd got hold of a power supply it came to life!

A quick play on receive and I found some cw, turning on the FT1000 MP and matching the incoming signal I could see that I was tuned in to 14.045 with the VFO fully turned anti clockwise, so I wasn't far off, the VFO toroid just needed some tweaking which was confirmed when I attached the MFJ 259 and using the frequency counter read that I was at 23.400MHz, just off the mark as the instructions quote 23.000MHz.

 So all I had to do was alter the gaps between the windings on the VFO toroid L114 to bring the frequency down to the required 23.000MHz as per the instructions. At the same time I had to tweek the caps for maximum power output between 100mv and 400mv, but this was fairly easy using my DMM. Once happy with the toroid readings it was a case of pinching some of my XYL's clear nail polish and giving the toroid a good coating and leaving for 24hrs!

 The toroid at L114  that needed a tweak

I must admit the hardest part I have found with this kit is the alignment, I've had little experience of this process but with the help of the instructions I managed to get through but it took time. You have to have a frequency counter and a DMM for this project and to be honest I'd never used the MFJ as a FC so it was all new to me and there are no instructions in the MFJ manual about how to set it up for frequency counting. In the end I attached a short piece of coax fitted a PL259 to one end and trimmed the earth off the other end leaving just the central wire. By chance I had a very narrow metal tube that fitted over the wire giving it strength and hey presto it was an excellent probe.

 The homebrew probe attached to the MFJ

The radio is now virtually complete except for the optional LED that I have to fit. I've had a good play but I haven't attempted a QSO yet, hopefully this will be done over the weekend. It's putting out a healthy 7 watts on the dummy load, but I've reduced this to 5 for QRP. First impressions are that the receiver is excellent especially when using the bandwidth, it certainly matches up to other radios I have owned. The 10 turn pot although smooth gives you little idea where you are within the CW sector of 20 meters so I suspect I will purchase the OHR Digital Frequency counter to make life a little easier.

Overall I'm really pleased; I've come along way since the early days of the RM builds and my confidence as a QRP builder has grown dramatically. Reading the reviews on Eham, the kit is probably classed as an intermediate, so hopefully I've passed with flying colours and now can look towards building my ultimate homebrew kit, the K2 !! 

In the meantime I shall enjoy working some QSO's with my trusty new OHR100A. Once I've added the LED I will post some pictures of the completed Radio.

OHR100A Build

Finally the OHR100A arrived but in the end I had to nip down to our local postal sorting office to collect it as they were complaining about how busy they were and it was going to take time to deliver. 

The parcel was well packed with individual sections of the kit separately kept apart which made things easy for identification. Marshal certainly makes sure of doing a good job in packaging as everything is nice and secure.

So the build of the OHR100A begins. To start with I thoroughly checked the inventory to make sure I had everything; I ticked off each part as I went and seemed to be all there so I could get on and make a start. I don’t plan to rush it; I’m going to take my time and build in roughly 2 hour slots so that I don’t over do it and make silly mistakes. The first part is to install several diodes and the IC sockets making sure that all are correctly positioned on to the PCB board before soldering.

The instructions seem very clear, certainly as good as the Wonderlabs notes which helps greatly when a newbie like me is attempting something a little more difficult than the RockMites. Amongst the instructions is an overlay sheet with clear diagram of where each part should sit which is very useful.

6 hours later and I’ve installed the diodes, chips, chokes, resistors, trim caps and capacitors, the only problems so far have been a slight issue with soldering as I’m having to re-apply a small amount on a few components to the top of the PCB board as the soldering is occasionally not penetrating through the holes, this is more likely because of the solder I’m using but in actual fact probably helps in double checking that everything is soldered correctly.

Approximately 9 hours later and I've all but completed the PCB board. Just the IC's to slot in to place and add in the Molex connectors. The toroids were a little fiddly but I think that is probably due to lack of practice and experience, but once I had done the first the others seemed to wind OK. 

Interestingly in the picture below you can see my one mistake that I had to rectify, which was placing the transistor D105 in to U104. As soon as I done it I realised my mistake but then had the job of carefully removing the transistor and then soldering it in its correct position. The one thing I've learned is that as soon as you feel at all tired take a break because that's when mistakes are made!

Now I have to assemble the chassis with all its components which hopefully won't take too long and then just wire up and do the smoke test.......More to follow!

Good News With the OHR100A

Well as soon as I started to worry that the OHR100A was lost forever in the vacuum of the postal ether I get a note from the Royal Mail telling me they have a package for me, but the bad news is I have to pay the sum of £35.50 for Customs and RM handling charges! £8 for handling charges, crazy! Anyway at least it's arrived and I know that soon I will  be once more happily getting stuck in to another building project.

The TH215-E has definitely shorted I found that the fuses J1,2,3 and 4 have all blown so something has caused it to fail. To be quite honest unless its a simple fix like an audio amp replacement I may just give up and buy myself another 2 meter rig off Ebay, we'll see.

Lost OHR 100A and TH-215E Problems

Still no sign of the OHR100A! I contacted Marshall at Oak Hills Research and he advised me to wait another week, before approaching USPS, but I have to admit I’m beginning to worry, I have ordered a few items from the US and they haven’t taken this long.

My only hope is that the package is stuck in the UK customs and it will hopefully arrive in the next couple of days. Looking on the USPS website Marshall kindly gave me a tracking number but all I see it that it was last seen in Jamaica NY on the 04/11, after that there’s no further information. It’s typical you build yourself up ready for your next project and then it doesn’t arrive!

Whilst waiting for the OHR100A I’ve been trying to figure out what is wrong with my old 2M TH-215E handheld. It switches on fine and even transmits ok but there is no sound coming from the speaker.

Using the MMD I’m getting output from the speaker and if I hold it close to my ear I can just make out the squelch, so I think it’s more likely it is the pot playing up. I’ve dismantled the radio and have attempted to give the pot a really good clean with some switch cleaning lubricant.

 The disassembled radio, on initial inspection all looks ok.

I’ve checked the PCB and can find no cracks or any sort of damage so at the moment I’m slightly at a loss as to where to progress from there. 

I've given the pots a really good clean but they are sealed units which does not help, so it's a case of gently feeding in the lubricant and turning the pot back and forth.

The speaker looks ok and I've checked the connections with the MMD and am getting output.

I suppose the options are that I make sure the extension speaker plug is not cancelling out the internal speaker, check all the traces to the speaker and last case scenario try and find another pot and replace the old one. ................Anyone had a similar problem let me know!

Audio Amplifier Kit

Still waiting for the Oak Hills Research 20 meter kit to arrive although strangely the LED kit turned up the other day, but nothing else. 

So I’ve been tidying up the shack and getting all my soldering irons cleaned up in readiness for the big day. I also purchased an audio amp kit this time with a bit more power 7 watts, my home brew audio amp is fine but lacks oomph. The new amp works well with the RMs and just means I can listen out to who is around when out of the shack in my other workshop.

I've also had ago at installing the CW filter I bought from Hamshops, and although it works  I don't think I've set it up correctly. when I add a 9v battery there is no change in sound so the small amp doesn't seem to be working. Without the battery the filter continues to work but all received signals are just quieter and there doesn't seem to be any filtering. I suspect when I originally built the filter I messed up the soldering of the amplifier hence its not working, however I will carry out further tests and see if I can find out the problem.

All three RockMites are now safely in the shack and used most days when I have the chance to play radio. I've had some good contacts especially with the 20 meter RM where I've gone over 1k miles which I'm pretty pleased about. The 30 and 40 get good contacts with Europe and the average distance is around 500 miles which is nothing to be sniffed at.

In fact the shack is looking pretty good a the moment and I'm amazed how it slowly filled up with various bits of kit. So I had a bit of a spring clean and re-organised things especially as I know I'm going to have to find room for the extra OHR 100A. In my haste to clean up I dropped my old Trio 2 meter handheld, it still switches on but there is no sound I've checked the speaker connections and they are all working so I suspect it's something a little more serious, never mind it will keep me occupied during those winter months, or it's an excuse to go out and buy myself a new one!

Do you like my old Royal Enfield in the top right corner?