Heathkit GD-1U GDO

Been to a few radio rallies and at the CDARC surplus sale on the 13 February I recently bought a Heathkit GD-1U Grid Dip Oscillator complete with the original coils, a bargain at £10.

SAM_5282 (Medium)

Thanks to Andy (G6OHM) for sending me the link to the service manual and David (M0ZEB) for the Assembly and User Guide.


GD-1U-GPO Assembly and User Guide (7.3Mb File).

GD-1A-GDO Assembly & User Guide.

MFJ 269C Pro Analyser

I realised fairly early on that I would need some form of antenna analyser if I was to build my own, the decision was then which one and how much to spend!


I opted to buy the MFJ260C Pro – Link to Manual as this has all the frequency ranges that I will need and a number of very useful, added value features, such as:
Coax Loss measurement
Cable Length
Length (distance) to open or short circuit
Capacitance in pico Farads
Inductance in micro Henries
Frequency Counter

The money to help pay for this came from not having to pay two months of council taxes, I ordered the unit from Ham Radio Outlet, New Hampshire, USA, their was a January promotion of a $50 reduction which eased the pain a bit!

The meter took 4 days to reach the Parcel Force Cambridge depot where it sat until I paid £64 release fee (£54 VAT and £8 handing fee), it would have been nice if I didn’t have to pay this, but I knew when I ordered it that it was a real possibility, nevertheless, I saved over £71.00!

Well I didn’t actually save £71 as the unit needs batteries to be portable, I bought rechargeable ones as I didn’t want to keep opening the case to remove batteries when not in use, also this allows me to regularly keep the batteries charged in-situ, the downside was that these cost nearly £30 – (10 AA 2000mAH batteries bought in packs of 4 from Argos).

I’ll give another write-up once I know how to turn it on 🙂

Noise Cancelling Speaker

After reading reviews and watching YouTube videos, I decided to buy a BHI noise cancelling speaker from Radioworld ltd – Link to Information.
I opted for this version as it has a small footprint and is very adaptable, for example if I choose to put a rig in a vehicle, transferring it is a very simple matter of unplugging the audio 3.5mm jack from the transceiver and 12v power lead, the other plus was that it has a 3.5mm mono headphone jack which cuts the speaker when plugged in, meaning the feed to the headphones benefits from the noise cancelling. (see warning)


The unit works really well and reduces interference and in some cases completely eliminates it enabling me to hear stations which I couldn’t otherwise.

The speaker has a number of controls:

Power Off/ Audio Bypass, with this ON the unit is a powered amplifier with the volume being adjusted but a control on the top of the speaker (Note – as a powered speaker it is susceptible to picking up the polling of any mobile phones near to the unit which can be very annoying), with the power on, but the noise cancellation OFF, a RED led will be lit on the front of the unit.

Turning noise cancellation ON is done by a slide switch on the top of the unit, the LED will change to green when in this mode, a multi-position rotary switch on the rear of the unit adjusts the level of filtering, you know when you have too much noise cancellation as the speech sounds like they are underwater!

I’m very pleased with the unit and it works well, two things I have found is that the filtering initially introduces latency during tuning until the noise cancelling stabilizes, this only takes a few moments but gives the impression that you are not on frequency with the tendency therefore to tune past the spot frequency in use, the other issue is that any roger bleep, radio confirmation or CW tone is not caught by the noise cancelling circuit and will break through the unit at an Warning – incredibly loud volume, be aware of this if you are wearing headphones (as I found out!!).

New Blitzortung Power Supply

Due to my previous blogs about a dodgy power supply unit (PSU) used for Chatteris Weathers Blitzortung lightning detector, I ordered a low electrical noise PSU off ebay.com, I ordered the 5v PSU on the 5th January, I received a mail confirming dispatch on the 7th January and on the 10th January it arrived from Hong Kong!

I plugged the unit in the detected signal quality is excellent, the PSU was quite expensive, but well worth the money as the performance of the unit is considerable better than before.
2015-01-09 23.54.24 (Medium)
Spot the spelling mistake 🙂

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5v USB at 1A and an output of 8.5v which I have used to power thermostat controlling the temperature in the small equipment room.

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TeraDak unit next to my NAS.

TeraDak PSU
Although ‘smoothing’ is on, the trace is considerably better than anything before it.

Lightning detection trace, picked up from Scotland, so not that far away.

CCTV Pan/Tilt Controller – Part 2

This is Part 2 from this previous thread, the remaining parts have arrived so I could complete the circuit which (hopefully) will give a relatively accurate positional indication, the circuit uses two LM3914 (one for Pan the other Tilt) with a potential divider signal being derived from the potentiometers (Pots) within the Pan/Tilt head, I have mounted the reference resistors slightly proud of the Veroboard as I’m not convinced that the values are correct, so I will be able to modify these from the top of the Veroboard.

Pan_tilt Leds
Circuit diagram of positional indication for the Pan element, for Tilt I have used three LEDs and so the wires from each LED will go to the appropriate leg of the IC which has the correct voltage when aligned to the correct position, a mod to make is to convert the mode of the LM3914, so instead of a ‘spot’ led indication used as in the direction indication, where each LED follows each other and then fades out, the tilt will show the LEDs staying on as the platform transitions from zero degrees to ninety degrees.

2015-01-09 23.02.15 (Medium)
Veroboard showing resistors raised for ease of modification should it be needed as the accuracy of the Pan/Tilt pots has not yet been confirmed.

2015-01-09 23.02.36 (Medium)
The Veroboard has been temporarily secured using a cable tie, this arrangement will be replaced with something more permanent when the unit has been proved in service.

2015-01-09 23.03.03 (Medium)
Connector block with two sets of three wires for the Pan/Tilt positional feedback Pots, followed by the Pan and Tilt motor drives and at the end, the brake release feed.

The supply is 24vDC which is reduced and regulated to 12v via board on the right, this is fully adjustable and will be used to tweak the voltages to make allowances for any external cabling voltage drops that are incurred at installation.

Lightning Analysis Reinstated

I have tweaked and restored the lightning analysis pages records_summary.php with the websites menubar link taking you to the records summary page, at the base of this page is a number of further links which drill into the details, (at the time of writing no new events have been generated since 2014).

The base program is called ‘Discharge’, a link to download this is on each lightning analysis page displayed.

General information and status updates.

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