Amateur Radio Homebrew (Shack Culture)

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Re: Amateur Radio Homebrew (Shack Culture)

Post by PanBiker »

Stuffed with exams for a day or two Stanley, but I will drop it off sometime. English Lit today, they don't like that one, extra paper at the ready. :smile:
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Re: Amateur Radio Homebrew (Shack Culture)

Post by Stanley »

I have UNC taps and dies...... But I still think it is a bastard thread..... (Yes, you are right, Unified Coarse as opposed to Unified Fine)
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Re: Amateur Radio Homebrew (Shack Culture)

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Pleased to report that I have sorted my transceiver.

I had a look at the desoldering base unit but really need a diagram to see the wood from the trees. It's internal circuit board is mounted vertically on a plug and socket arrangement and the board carries most of the circuit for the pump drive as well as the power rail generation, difficult to get to the back of it for testing. I have a functioning 24v supply from the front of the unit so I ran a length of twin cable up to the head and wired it directly to the heater leads, I put shrink wrap an the leads to make sure I had no shorts when I reassembled the head unit. The threads to hold the head into the handle unit were all broken out so I decided to make this a sacrificial repair by putting it all back together with Araldite Rapid. Heater and pump now working so I had high hopes of getting forward, Turns out that 15 years in the loft has not done most of the micro tips any good at all. I spent a good couple of hours trying to clear the tips of corrosion with the the cleaning tool to no end really, I only managed to get one back to reasonable functionality.

Final resolution came with a combination of vac pump, 1mm solder wick and then with heart in mouth and the biggest chisel tip on my Weller soldering station iron I dare offer to the board, I managed to clear the final 5 plated through holes by heating the pad and inserting a component lead, withdrawing it while the joint cooled. The holes were so difficult to clear as the pads are only 1mm with the plated through hole about half of that. Anyway, where there is a will there is a way. I cleaned the board up with PCB cleaning solvent then had a really good look on the reverse for any solder bridges or spats under my bench magnifyer. I thought I had managed to bridge a couple of pads on the tightly packed side of the filter with 3 pads so I checked with the meter, they were showing dead short between the two! I had a look at the PCB layout in the service manual. I could not see the connecting tracks on the diagram as it showed the lacquered view of the back of the board. The circuit diagram only showed three connections for each of the filters, input, output and ground. The filters each have 5 pins, 3 on one side and two in the opposite side corners. I went onto the filter manufacturers website and looked at the technical specs and was pleased to see that the two corner pins were the input and output and the three on the opposite side were all connected to ground. A quick check with the meter on all the triple sets pads on each filter confirmed they were all connected to ground. What I had actually done was remove the lacquer between the two pads during desoldering, exposing the copper ground plane below which I had managed to tin at the same time!

I installed the three new filters, double checking that I had them all in the right order, (they are each a different specification) before soldering them up. Another quick flux clean and then rebuild, the board has two areas that sit on flat raised areas of the chassis as they need thermal coupling for the mounted components. I renewed the heatsink compound on these pads before screwing the board back into place and reconnecting all the leads.

It's a different transceiver! Not surprising really as the leaky filters were attenuating the IF stages of the receiver. Two out of the three looked to be contaminated which was borne out by the previous performance on the mid and high bands. With the fault a local signal although audible would not register anything on the signal meter and at best could only be reported as a fraction of its actual strength. Same contacts now show as they should as full power and fully quieting the receiver. Receiver sensitivity is back to optimum but has shown up another slight problem which will mean the lid will have to come off again at some point.

Chattering Squelch!

Squelch in its simplest form is a system that allows you to mute the receiver noise in the absence of an actual signal. It's a rotary control on the front of the transceiver which should operate with a clear cut off point. The increase in receiver sensitivity has shown that this is no longer the case with my squelch control. You can set it but it has a tendency to drift on the threshold so you have to adjust it again. There is a simple mod for this which involves fitting an extra electrolytic capacitor across an existing surface mount device. The existing SM capacitor is on the top side of the main board that I have been working on and is directly accessible so It's just a case of tacking an extra one of the right value directly across it.

There are different uses for squelch circuits, Wiki is below for edification.

Squelch
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Re: Amateur Radio Homebrew (Shack Culture)

Post by Stanley »

Once again, all Greek to me but Impressive Ian.... Glad you got there in the end!
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Re: Amateur Radio Homebrew (Shack Culture)

Post by PanBiker »

A bit of spare time yesterday so I set about the modification for the squelch control. I disconnected the multiple connectors from the transceiver and got it back on the bench. Lid off and a couple of internal connectors to disconnect for the speaker and battery control. Although I wasn't taking the board out from the chassis I still connected it up to the earthing mat and wristband to do the soldering. An easy job as the target capacitor for bridging is on the top of the board, hardest bit was getting in at the right angle between the other component to tack the extra 4.7uF capacitor across the SM one. Managed OK though so I put it back together and reconnected all the leads. Pleased to report that the mod does what it says on the tin, the control now has a definite cut off threshold with no chatter and will still trigger on the presence of a signal (even the weaker ones) so a good result.

A couple of mates are operating from Settle highside in the 144Mhz low power contest today so I gave them some points with my IARU locator (Maidenhead) square (IO83VW) and a report and serial number. The contest is for stations running a maximum power of 10W (all modes), points multipliers are given for the number of different locator squares the can be contacted. I know their operating location well, my mate and I came 3rd in the very same contest back in the late 1980's.

Maidenhead Locator Wiki

WhatsMyLocator - this will display you locator by entering a postcode

I have also been revisiting various data modes and have made a start on reconfiguring the transceiver settings for interfacing with my computer. I have done both a factory reset on the transceiver and have a different computer now from when I first put the station together.

I need to get the baud rates and handshaking protocols configured properly so that I can get two way control between the data software running on the computer and the transceiver. I have the receive set up and the transmit / receive switching works OK but I need to brush up on the CAT control as I can't yet control the tuning on the transceiver from the software on the computer. It should work both ways but it's not at the moment. I think it's something in the menu settings on the transceiver that's been set back to default

I have been copying RTTY transmissions OK and the software is decoding fine via the USB Signal Link interface. I can see transmissions from all over Europe so that side is working fine. I will have another go at it now I am the right side of a bit of lunch.
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Re: Amateur Radio Homebrew (Shack Culture)

Post by Stanley »

:extrawink:
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Re: Amateur Radio Homebrew (Shack Culture)

Post by Big Kev »

I'm with Stanley, it's all Greek to me but it makes good reading :-)
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Re: Amateur Radio Homebrew (Shack Culture)

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PanBiker wrote: 11 Jun 2017, 13:32 It should work both ways but it's not at the moment. I think it's something in the menu settings on the transceiver that's been set back to default
Big Kev wrote: 12 Jun 2017, 10:56 I'm with Stanley, it's all Greek to me but it makes good reading :-)
Well, what can I say apart from it's all Greek to me sometimes as well. :extrawink: I had convinced myself it was a configuration error and spent an hour chasing my tail instead of chasing the other end of the serial lead between the transceiver and the computer. :surprised: Not plugged in!

Not really surprising though as it now has the wrong connector on for my firewall box that I now use instead of a conventional computer. The lead terminates in a proper 9 pin D serial connector which was fine for my old computer. The firewall box only has a single USB socket but I have expanded it with an eight way USB hub. I will need a completely different lead as it will require isolation components built in to stop the voltage on a USB interface getting back to the transceiver. After suitably kicking myself I have ordered the wherewithal online and It should be delivered in the next couple of days.
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Re: Amateur Radio Homebrew (Shack Culture)

Post by Tripps »

That made me smile Ian.

I thought only I did things like that. eBay will sort you out. :smile:
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Re: Amateur Radio Homebrew (Shack Culture)

Post by Stanley »

For a parallel, have a look at the way I am struggling to understand what happened to my bloody crankshaft! I am dreading starting cutting and have thought of one more improvement I can make to avoid what I think was the the trouble.

Image

If I can make these where's the problem?
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Re: Amateur Radio Homebrew (Shack Culture)

Post by PanBiker »

New replacement lead has arrived, see Radio Station Rebuild
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Re: Amateur Radio Homebrew (Shack Culture)

Post by Stanley »

:laugh5:
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Re: Amateur Radio Homebrew (Shack Culture)

Post by PanBiker »

Plans are afoot and I have ordered metal in the shape of 1/4" aluminium bar. It will be cut slightly oversize for the lengths I need, less than a fiver for the stock to make two. I'm going to build a Moxon. :cool4:
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Re: Amateur Radio Homebrew (Shack Culture)

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Moxon. I had to look it up. Link. .

The Moxon antenna or Moxon Rectangle is a simple and mechanically robust two-element parasitic array antenna. The design is rectangular, with roughly half the rectangle being the driven element and the other half being the reflector. It is electrically equivalent to a two element Yagi antenna with bent elements and without directors.

The Moxon antenna is popular with amateur radio enthusiasts for its simplicity of construction.
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Re: Amateur Radio Homebrew (Shack Culture)

Post by PanBiker »

Correct P. I am going to play around with 2M (144 MHz) versions. I will need some 15mm plastic pipe and T connectors as well as some acetal bar for the portable design I am thinking about. It will be good for carting to the top of hills. Here is the utility that calculates the dimensions for any given frequency and element size used. It's set for 144.3 Mhz which is the centre of the SSB portion of the band.

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Re: Amateur Radio Homebrew (Shack Culture)

Post by Stanley »

All Greek to me but I am impressed. How are you at wiring up reversing switches?

Image

I have this very good reversing switch which I know is right for the motor on the 1927 lathe as it was originally fitted to it. I need it for threading and other matters but wiring it is beyond my pay scale! Any thoughts?
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Re: Amateur Radio Homebrew (Shack Culture)

Post by PanBiker »

Never done one as I am not an electrician. I do know there are lots of variants for reversing motors though. Is it a single phase supply and motor and does it have a connection crib on it by any chance?

Contract electrician territory who would also have access to the correct cabling for the job.
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Re: Amateur Radio Homebrew (Shack Culture)

Post by Stanley »

Single phase 1/3hp Horace Green, newly rewound and rewired. No crib in lid but new wires clearly marked. Lots of wiring diagrams on web for the Dewhurst drum switch. Including a Youtube one if you look it up.
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Re: Amateur Radio Homebrew (Shack Culture)

Post by PanBiker »

Yes and also a lot of warnings about using old switching gear, arcing and bakelite degradation seem so be the main concerns. Competent but not qualified for this and it would be bad practice to fit what is essentially obsolete equipment with the associated risks. Serviceable modern equivalents are available but you should still use the services of a qualified electrician to be safe.

If it was originally fitted, why was it taken off?
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Re: Amateur Radio Homebrew (Shack Culture)

Post by Stanley »

Don't know, the lathe wasn't dismantled by me. It was on when Newton used it. I'll look for a Sparks.....
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Re: Amateur Radio Homebrew (Shack Culture)

Post by PanBiker »

Just adds doubt that there may be something wrong with it. Not the kind of thing you should take chances with, switching mains voltage attached to a large chunk of metal, it needs to be right.
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Re: Amateur Radio Homebrew (Shack Culture)

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In the wait during researching and gathering bits for my antenna project. I have done a bit of a repair job. This was in the shape of a 10 band transistor radio that was dead in the water. At first I thought that it was just the batteries but swapping them out made no difference so up onto the bench it went. It's a smallish job about 6" by 4" but has LW/MW/VHF FM and 7 Short Wave Bands so worth ressurecting just to see how it performs.

I took the back off and then removed the chassis from the front case, this took a bit of doing as it was held in by multiple plastic clips around the edges and some through the PCB. Handy though that the battery compartment (3 x AA) was integral to the chassis so it was one solid block. I got the meter out and tested the slide switch for the power on but could get no continuity reading so I de-soldered it and whipped it out. Tiny thing only about 10mm in length but I noticed it was a simple sliding leaf switch which could be dismantled if push came to shove. I flooded it with switch cleaner and switched it a few dozen times then flushed it again with the aerosol cleaner. I offered it up to the meter and normal operation was resumed. I shoved it back in, re-soldered and put the batteries back in, it was still dead. I tested with the meter across the feed points from the battery stack and got no voltage reading?

Closer inspection showed that the spring metal plate for the positive connection from the stack was slightly corroded. I tried cleaning it up with by fibre tipped cleaning tool but still couldn't get continuity. The plate was soldered with two tabs to the edge of the circuit board so I took it out for a closer inspection, the surface was pitted with the corrosion but the other side of the plate was as new, simple matter to bend the fixing tabs the other way and use the other side of the plate for the battery contact. I soldered it back in and reinstalled the batteries, checked on the board that we had 4.5v which we had. Normal operation restored. I rebuilt it all and tested it on all bands, it works well for such a small portable. It has a stereo decoder for VHF FM although you would need headphones to benefit. Anyway it's fully working again.

I was trained in electronics in an age when everything was repairable and must have done hundreds of repairs on tranny's in the 70's and 80's. One of the best ones that was brought in was a late 1950's classic, a Bush TR82C. This was one of the first British transistor radios and has become a design classic, so much so that they still produce replicas of it today. I have a later version of it on top of my freezer as our kitchen radio. Anyway this particular one was trotted in by one of our farming customers. He looked bereft as he carried a cardboard box up the steps in the shop to the counter. "I hope you can repair this for me, I have been listening to it for over 25 years, I have it on my tractor but it dropped off and I ran over it!" I looked in the box and sure enough it looked like a radio that had been run over. The case was smashed off it and the metal chassis that the components were mounted on was bent into a V shape, the battery connections were ripped off and the whole job lot was covered and embedded with the chunk of field that he had compressed it into. I could actually see that some of the capacitors were flat with their guts hanging out, odd resistors were broken in two from their mounting posts. "Please can you fix it, it's been a good friend", I gave the bloke a wry smile and took the sorry mess of him and said I would try my best.

The radio was built with point to point wiring of components on chassis mounted pillars on a mild steel chassis, no PCB's used in this design. First job was to get the muck off it so I extracted the chassis gubbins from what remained of the case, took it in the back yard and turned a water hose on it and gave it a good wash. I put it on the storage radiators to dry out for a couple of days then assessed the damage. The rotary on/off switch and integral volume was smashed so I fitted a replacement control and a separate toggle switch on extension wires. I replaced about 3 crushed capacitors and a few broker resistors and rigged up a new battery compartment on wires. I hooked up the speaker now detached from the case which had miraculously escaped the crushing. I shoved some batteries in and switched on. I couldn't believe it, it worked!

I rang the bloke up and he was elated. I told him that it was functional but it's portable tractor days were over. I fixed it all in a new cardboard box and secured the various bits in with insulation tape. I charged him a fiver for the repair which had become a bit of a challenge for me, he was made up! The set was retired to the miking parlour and I know that it ran for at least another 15 years, he was still buying batteries for it when I left the trade and moved into computers. For all I know it may well still be working. They don't make them like that anymore only modern replicas. :biggrin2:

Bush TR82C
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Re: Amateur Radio Homebrew (Shack Culture)

Post by Stanley »

I have a Sony tranny and tape player in the shed that has done over 20 years and always in bad conditions.....
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Re: Amateur Radio Homebrew (Shack Culture)

Post by PanBiker »

Back on track, I nipped over to Burnley yesterday to pick up my aluminium bar. It was ready for me and packed for transportation in a 2m length of angle iron wrapped in industrial cling film, no charge for the angle. I called in at Screwfix next to get the bits for the hub, I have bought 2m of 15mm PEX barrier pipe, 5 x JG Speedfit 15mm equal T's and a pack of 10 plastic inserts for the pipe ends. The plastic bits cost 3 times as much as the metal!

I was chatting on the local net on 144Mhz last night and asked for advice on how to get as near to a 90 degree bend in 1/4" aluminium solid bar, I have 4 bends to do and they need to be pretty accurate as they dictate the overall dimensions of the antenna which will determine the resonant frequency and the impedance matching.

Fortunately Fred (2E0ZTM) called in to the net, he is a metalwork fabricator and gave me some tips, he said it would be best to anneal the forming point and had a tip for using Imperial Leather soap as a temperature indicator. Apparently you rub the area to be heated with the soap and then heat until it turns black, you are then good to go and should be able to form without fracturing the bend. Fred picked my brains on filter replacement for the FT897 he has the same transceiver as me with the same problem I have recently fixed. Knowledge exchange, someone always has the answer. :smile:

A question for Stanley before I order my engineering plastic. Probably a daft question but can you machine Acetal rod?

Technical spec from Direct Plastics:

"Acetal is easy to machine
Acetal Rod is probably our best machining engineering plastic. It makes the machining process very easy by chipping rather than creating a continuous length of swarf that often wraps around tooling. By using very sharp cutting tools that are designed similar to smoothing tools, Acetal Rod can be machined to an outstanding surface finish with machining marks barely visible."

Acetal has the best electrical properties for my usage and has good moisture resistance. It will need the diameter turning down slightly and a 1/4" hole poking through the centre. A couple of pieces will need the holes drilled to a specific depth from each end. They will effectively be for bushes in the T pieces that the hub is formed from.
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Re: Amateur Radio Homebrew (Shack Culture)

Post by Stanley »

I'd be surprised if I couldn't!
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