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Saturday 30 January 2021

AC unit replacement.

Looks like AC has failed in shack so neither cools or heats now.

Right now operating without any heat in shack is a tad uncomfortable after a while.

The AC unit is an old eIQ-12WMINV the original gas was replaced with a new refrigerant a while back. Anyway the comms from the inner and outer have failed so time to get a new one. Done that but now it seems that the local AC guys that installed the previous one will not install this one as they didn't supply it, and as not prepared to pay a 150% mark up for the same unit just because they order it so a bit stuck or am I?

This is <7KG of R290 so doesn't actually need you to use an AC company. Not sure that is the wisest option but it looks like the locals have given me have no option but to commission this myself.

Why would I even think of doing this?

After recharging my dad's car AC and knowing all the kit still exists and having worked with gas lines, pumps and gauges and CFC's when I did my PhD for years I thought why should I not try and DIY this?

I got lots of hints and suggestions from others with similar units and this is what this post is about.

I have this kind of manifold gauge.

So worked out this much...In summary, inside unit is charged with nitrogen. Outside with refrigerant. So let the nitrogen out, connect the pipes. Then vacuum the whole lot inside and connect the outside.

These units are all supplied with refrigerant contained in the outdoor unit, so as long as don't open that it stays there.


You need to purge the other pipework of all the air. I have a vacuum pump to do this first down to about -30 PSI. Once done and connected up, and tested there are no leaks in the pipework, will do this two ways, one see that the unit holds the vacuum for a while and second to pressurise it with N2 as well and monitor the pressure levels on both occasions, open the outside unit gas line (containing the condenser), with the AC unit turned on and set to cool that will then draw/fill the gas lines with refrigerant and the AC unit will then work as planned.

I was told that without a pump and specialist A/C kit as this is new it is still possible to connect things up but you can risk losing too much refrigerant. If you do that you will probably need an A/C engineer to refill your unit properly. Think lots of costs.

However, it is not impossible, definitely not recommended but if no other options and if you are prepared to risk this the steps might be these. With the inner unit set to run cool then once you have tightened up all the joints fully on the gas lines then use a 1 second fill from the liquid valve with refrigerant, that is open the valve, having first got ready with leak spray or soapy water and a brush. You need to test all your joints several times with spray and listen and look for a serious leak. You might need to repeat a few times if you do find a leak but when satisfied with all of the joints you need to work out carefully the path of the refrigerant from the outdoor unit, through the indoor unit and back to the outdoor unit . The end of this is the T shaped valve on the outdoor unit. Take off the plastic cap on the T to reveal the schrader valve. Open the liquid valve for an other 3 seconds (you must hear the system filling up for 3 seconds) Close it and leak test the joints again.

Then with both valves closed, press in the schrader valve to expel air and refrigerant for 5 seconds. You will possibly see some oil deposits and aget a cold blast. The pipework is now full of refrigerant in gaseous form. Now open both valves fully and replace the purge cap. The system should now work.

However, this is a warning.......not using an Fgas engineer will invalidate the long term warranty of the unit and if it all goes wrong you will have to call one in anyway.....not cheap if they will even look at DIY units with R290 refrigerant (which is basically refined Propane so very flammable!). There is a very very real chance this could all go badly wrong with R290 as this ia a refined version of the same stuff you will find in camping gas and the AC unit has aboiut the same as two of those small cans so the result could be very bad. This is perhaps why the non technically minded, those without any tools should probably not even attempt this and go with an FGas engineer.

Anyway waiting for a period of drier weather and will go through the process.

(and I guess any comments to pick up if I had missed anything)

Saturday 16 January 2021

New 13cm pipe end cap filter

Components RG402 semi rigid, piece of FR4, SMA connectors, 3-22mm pip cutter (to score the shield before removal), Brass M3 nut and bolt (should be M4 but don't have to hand).

Holes are 3mm (initially, filed out to have a tight fit about RG402 sheath. 16mm apart.

It's a 1" copper end cap. So much larger than the 10GHz ones you might have seen using the 1/2"/13mm end caps. But the principal is the same.

The RG402 make up isn't hard.

You take one end and strip off the teflon insulator and trim the centre conductor to about 4mm and fit a pin over.

Then solder on the other part.

Then solder into the FR4 (the shield remains below). I'll trim the probes to about 8mm before filling the cap.

You then solder on the end cap, first soldering the brass nut on the central hole so the brass bolt can be screwed in and out and secured by the second nut, I might add a red locking liquid (nail varnish works if the XYL has some she will not miss!). You tune by advancing this bolt. The more you advance the higher in frequency the filter tunes.

The soldering of the brass nut and pipe end requires considerable heat, I have a small precision (bit of an oxymoron when talking about a blow torch!) blow torch I use this this work.

I will make up and add the NanoVNA 3GHz scan image here, basically when tuned it will allow the 2.4GHz signal to pass and block frequencies either side, like mixing products. 

Thursday 14 January 2021

New hexbeam /Dipole 1:1 FT240-43 balun

Decided to make up the DX Hexbeam and Dipole 1:1 FT240-43 balun that had been knocking about for a bit. Based on the W1JR version.

Rather than fit SO239 or N Type sockets going to add pigtails using N-Type compression fittings.

Coax is teflon cored RG-142. Not 100% it is the correct stuff to use so once made up will put it on a VNA.

HP360 Power Meter FR4 case

 Just pulling together putting this into a case I'll make from FR4 offcuts.

Will add 3 push to make switches an on/off, external DC feed and will add an external SMA.

getting there, bit bigger than just the HP360 but will fit something else in the case too.

Lid (no photo just yet) will be added and the HP360 will screwed into it.

The switches a DC connector I'll fit to the base before hand. The remaining space will probably be taken up with a simple VSWR meter.

Tuesday 12 January 2021

Mast clamps

Will possibly save using so much electrical tape putting up the masts.

I use telescoping fishing poles a lot and one issue I notice is that I can end up using a lot of electrical tape to secure the sections. Investigated a few options, including using square section rubber tube (with 4mm releasing cable ties inside) which works quite well. Got to thank TX6G for that hint.

Investigating another option and making up some make clamps from old cycle inner tube, heat-shrink and stainless hose clamp set, you cut the clamp to length.

Raw materials:

First clamp (for base section): Not perfect, I'll get better!

It is a layer effect... heatshrink about some cycle innertube, the clamp runs through so the mast will have the heatshrink and rubber between it and the clamp.

You cut the rubber and feed it through first then the clamp section and then heat it into place. Feed the tail into the end and feed it in.

Saw something like this on M4A, G6UW antennas a while back and 'found' I had a bag of bits to make it and through might be fun. I expect need to add some labels on them with white permanent marker and short length of clear heat-shrink over?

One down, 11 sections per 10m travel pole to go, few less on the longer masts.

Got 70 odd clamps and the metal strip you cut to length and plenty of old innertube and heatshrink.

I have a 7mm hex driver, I need to get a 6mm one for these.

Should make fixing the masts a bit easier. Might not be faster.

I think Spiderbeam or a DL had a similar website.

Monday 11 January 2021

HP 360 RF Power meter

Grabbed a 16x2 LCD from the junk box and and added some inpin pins so it plugged in and then to the SMA input port added a couple 3dB attenuators before a small signal generator and fed it in and it seems to be working fine.

The RF Power Meter is rated at < 1W input but it is capable of up to 2.49GHz so should do 13cm even.

Now to box it up properly.

Saturday 9 January 2021

GM328 Put into case and initial tests

 Ran it off a desktop power supply measured at 9.1V DC.

Screen reports 9.1V DC.

Ran through the self test using 100nF capacitor and a set of joined wires to short probes 1-2-3

A 33nf capacitor with this reported as 33.29nF which tallied with another tester.

Bit cold in workshop right now so will post a few more images of random junk box/salvaged components then pick this up another day but on face of it seems to be working fine.

GM328 Build board stuffing.

 Just followed the silkscreen placing components.

Not terribly difficult. The  Pins on the uPC were a bit bent but straightened fine.

Noticed a few things missing.

One 27K resistor and couple terminal blocks.

Thursday 7 January 2021

GM328 Clone Build.

 Having bought one of these cheap component testers from China (I assume) I will blog the build here.

Images to follow.

The manual I found separately here

There is a nice youtube of someone reviewing it here or another here