Wednesday, 29 July 2015

First 144MHz EME QSO

After spending much of today removing my 4/6m yagi from the mast in order to put the 144MHz yagi back up I was rewarded with my first 144MHz EME QSO! 

Almost predictably the QSO was with I2FAK. Using 200W of JT65b to a YU7EF and one of my PGA144 preamps, Franco reported my signal at -21dB and he was up to -15dB with me, averaging -18dB.

I also saw an S5 calling G0GXT and PA5Y working I2FAK.  PA5Y would have been workable although his direct signal was close to and many dB stronger than the reflected signal.

The big change from previous attempts at EME on 144MHz is that the YU7EF now has a straight dipole rather than the folded dipole that had caused me so much trouble with a poor match. I have a second to add to the array at some stage.

The moon was one day past lowest declination, so at the time of the QSO, the elevation of the moon was about 15 degrees at an azimuth of 150 degrees. I suspect lots of ground gain this time!

That is now 4 bands on which I've had EME QSOs (2m,  23, 13, & 6cm) and I've heard signals on 9cm and 3cm.
Hopefully I will add these two latter ones as worked in due course and add 70cm at some stage.


Friday, 24 July 2015

Amsat Colloquium

Mainly getting ready to go to the Amsat Colloquium in Guildford tomorrow.
Early start but that may mean braving the stormy weather due to pass over this area tomorrow morning around the time we are due to start out.........

I met up with VK5DK from Mount Gambier, South Australia, today. Colin is visiting the UK with the Victoria State over 70s cricket team. Their game in Ipswich, today, almost didn't happen due to rain. But they managed to get in a few overs before calling it a day! Colin and I had the chance to chat for an hour or so. Last time I saw Colin was in South Australia some 6 years ago.

Although Mt Gambier is actually in South Australia, the tour captain told me they designated anything east of the Murray River as still in Victoria. That way they were able to include two people from Mt Gambier.  I guess it is getting difficult to find enough players over 70 to include in their touring team!


Friday, 10 July 2015

More EME dish

Whilst writing this morning's blog I realised I hadn't updated the EME dish story.
I have now used the 2.3m dish to receive the the DL0SHF 3cm beacon reflected off the moon. I've also received JT4F signals from G3WDG at around -6 dBJT ( dB below 0dB in 2.5kHz)
This is quite good but several dB lower than I would have expected. My tracking is still being refined. 

After my initial euphoria at being able to find moon noise, later tests showed it to be a lot more difficult to find when the moon was at low declination and was close to trees etc, possibly indicating a bit more  ground noise that there should have been. Whilst the moon was at low declination I took the opportunity to change the feed for the 23cm one to check this was still working. It is three years since I last made a 23cm EME QSO! The reason being the need to move the dish to a new location in the garden after my neighbour's extension went up and blocked my moon window from anywhere west of south. No NA stations west of the American East coast..... The new location is more prominent, but gives a longer moon window.

My attempts to improve the cage alignment seem to have paid dividends as I now get more sun noise to to cold sky on 23cm than when I was last active on the band. And yes, this is taking into account the currently higher solar flux!


Transverter follow up

I have commissioned another batch of Anglian transverters from my 'assembly' man!
Of these most will be for 2m, but a significant number will be 'uncommited' boards that can be either 2 or 4m ( or any other band between 220MHz and 30MHz).

As the noise problem on 4m hasn't proved to be a big problem when beaming between east through west it has not impacted my SpE activity on 4 or 6. 
DXCC and locator scores have been steadily increasing.

I am off to the Finningley Microwave Round Table on Sunday. My intention is to take a small number of various kits including the very last one of the current batch of Anglian 144MHz transverters. I will also take PCBs and devices for sale as spares or as required. As always, I will be taking the ever-popular WA5VJB PCB antennas, covering all frequencies from 400MHz to 25GHz.

Hoping to see lots of microwavers at Finningley on Sunday.


Monday, 22 June 2015

Eme dish again

I have made a bit more progress on my EME dish refurbishment.
The dish is back on the mount and the quadrapod is also in place and connected to the feed point cage.
Thanks to G4DZU I obtained a length of flexible 4 inch ducting to carry the coax cables and DC control cables between the dish and outdoor shack. The duct has yet to be buried.
I've also managed to mount the weatherproof Storno case to a suitable bracket and to the dish support pole. The various DC cables are currently terminated in a plstic box. They will be moved to the Storno case together with a voltage converter module to 12v from 28V.
There still seems to be a lot of work to do to get the dish ready for EME.


Saturday, 30 May 2015

4m transverter

Although I haven't advertised them, I have been making 4m versions of the Anglian kit available.
Since getting back from Dayton I was determined to finish a new 4m transverter incorporating the Anglian module with one of the 30W Mitsubishi blocks. This is destined for a customer of mine.
I finished the transverter last night, just in time to take it to the Codgers breakfast this morning.

After a few tweeks to the grounding around the module and replacing the cheap Chinese power lead ( it came with a moulded plug and socket) I am now seeing over 50W saturated output. At 30W PEP the output IMD seems to be quite acceptable.

Unfortunately my QTH seems to suffer an abnormally high noise level on 4m. It is far worse on 4 than on either 6 or 2m. The noise level increases over 10dB in all directions away from due south.
I think it is time to do some serious investigating as I really would like to get back on 4m myself and I still have one of my original Nacton 4m transverters and a 150W SSPA. Nice!


Wednesday, 27 May 2015

PCB made

Well, I etched my first PCB in several years. I'm pleased to say that it was a very clean etch in spite of some reservations I had about the old sensitized Photoboard 2 (6 years old!) I had used and the two year old developer. That developer has now been ditched and a new batch made up. I' e also bought new sensitized board.

Tomorrow I intend making up the 4m 30W PA. my plan is to finish the transverter by this weekend as I want to use it in the present good ES conditions.

I had a disappointment with the Magnetic Devices 951 relay I had intended to use in the transverter. It turned out to be a 24V rather than a 12v coil............the 700R coil should have told me that!

To overcome this problem I started to look for a suitable circuit to drive the 24v relay coil from the transverter 12v supply. I did not want to use a voltage converter as there is a potential for audio frequency spikes causing interference. 
An alternative solution is to use a circuit like the K04BB all-DC circuit. This circuit charges a rather large value electrolytic capacitor to 12v. When you want the relay to operate, the charged capacitor is placed in series with the 12v supply to give 24v. Although the capacitor will discharge rather quickly as the relay is operated, the remining 12v is sufficient to hold the relay operated. 

The disadvantage of this circuit, as shown, is that it is not possible to operate the relay with a press to talk ground connection. Usually an isolated relay contact is used to apply a positive voltage to the 'trigger' input.
I didn't want to use a relay so I thought it might be possible to use an Infineon high side switch MOSFET to do the same thing, but with a ground PTT input.
I am pleased to say that this worked extremely well. I was wary that under certain conditions it might be possible to defeat the circuit by rapidly switching between on and off. I'm pleased to say that with the relay and circuit component  values that I used it was not possible to defeat the circuit!
I'll publish the circuit on my web page.
I will be making a printed circuit board for the relay circuit as my first new PCB with the resurrected PCB facility. I see this could be a very useful board for all sorts of uses!