Category Archives: Radio Ham

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)

NES10-2-MK3_2c54ce28c0a1105603d6ff099dbb7676

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 please 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!!).

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.

Electrical Interference – The hunt with my mate Billy.

I have had a problem of a really strong pulsating radio interference signal lifting my noise floor, the strongest signal were at 350Mhz, 521.5Mhz, 924.7 Mhz, 990.3Mhz, 1.802Mhz, 145.537Mhz and 145.000Mhz detected by my trusty AM radio, Billy.

SAM_5244 (Large)Billy the Fish with a broken gill.

Preliminary investigations walking around the house and outside pointed to it being the neighbours solar panels as when I got near to his garage where the inverter is located, Billy went nuts, it was as though it was radiating out everywhere, putting Billy over my buried radials in lawn amplified this signal up, even putting the radio near the earthed outside tap picked the interference up.

As I was convinced the interference was from outside of my house, the only way to prove this was to turn the power OFF to the house, so with Billy in hand, I turned the power OFF expecting the radio to go quiet, but it didn’t!

Looking around in the garage, where I turned the power off, for a source of the noise, I saw the UPS for the PC was ON, turning this OFF the noise reduced, but still did not stop, walking around with Billy the interference was still very evident.

Went inside the house and heard two other UPS bleeping, the first one is in a room directly above the garage and as soon as I turned this OFF the majority of the noise stopped.

SAM_5251 (Large)

The next visit was to a room off my home office where my network kit is installed, the main UPS is fitted there, turning this off and the radio went dead quiet, so much for my theory of blaming the neighbours solar panels!!

SAM_5246 (Large)

So now to start turning things back on, with all the breakers off, I turned the main power switch ON, and the radio stayed quite, turning the breakers ON one by one, I didn’t get very far until the radio kicked off again.

First breaker causing a problem was the garage sockets, turning the switches on the sockets OFF in turn, I came to one which stopped the noise when turned off, it was a 12v switched mode power supply for a camera causing the interference.

The next breaker to cause me a problem was the one to the house sockets, switching this ON, yet again caused the radio to detect interference, back into the house with Billy, the hunt was on!

It turned out to be right under my nose in the office, it was the Blitzortung lightning detection controllers power supply unit.

SAM_5243 (Large)

I will investigate sourcing a low noise 5v DC linear PSU as well as making improvements to the controllers earthing as I don’t want to disable the unit.

I do have background hum from the power supplies feeding the Netgear switches and other small load items, but it’s nowhere near as bad as it was and I know what’s causing it, which is good, total elimination is the optimal solution, but proberbly unrealistic, so bit by bit I’ll chip away and get the noise floor as low as I can.

CCTV Pan/Tilt Controller – Part 1

A good friend of mine asked is I could get him a CCTV Pan/tilt head so he could remotely control the position of his aerials which would be especially useful in the tracking of satellites, some time later I noticed that a guy was upgrading a CCTV system, I went over to him and asked I could have the scrap head, came home with it and straight onto the internet for the make and model, but more specifically the wiring details.

The one I obtained was made by Shawley Antony Ltd who are no longer trading, but the head works just fine on 24vDC with the added bonus of having electromechanical brakes for both Pan and Tilt and having potentiometers so that I can have a go at getting positional feedback displayed.

In order to make a decent project I used Ebay to get a joystick, Pulse Width Modulator motor speed control and a voltage reducer all from China at silly prices.

I created the personalised overlay using Visio, this allows me the layer the drawing and the dimensional drilling detail can then be used to template the drilling pattern before being turned off, and the finished overlay printed.

SAM_5220 (Medium)Control Unit under construction

The way the controller will work is via a 24vDC supply, the 5vDC regulator will provide power to the LM3914 which will be configured for spot display of voltage derived from a potential divider circuit using the head pots, the LM3914 will drive the LEDs indicating the compass positions, I’m not sure if this will work accurately reflecting the head position, but that will be for the next part of the blog when the parts arrive. A similar arrangement will be used to drive the three LEDs showing if the head platform is at the horizontal, transitioning or vertical plane.

The switch marked Pan/Tilt Power, when operated will release the head brakes and light the associated LED, also, power will be applied to the speed controller enabling the joystick to operate the head at a variable speed set by turning the Speed Control knob, the advantage of using a pulse width modulated speed controller is that the motor does not lose torque at low speeds and will therefore not ‘stall’ under load.

SAM_5221 (Medium)Awaiting parts to complete the controller

The picture shows the internal setup for the motor left/right/up/down movement which is operational, the flying leads have been attached to the LEDs ready for the next stage…Watch this space for the next installment.

Link to Part 2.

WSPR – Propagation Report on 10 Watts

Now revision is over, I’ve been playing with WSPR (Weak Signal Propagation Reporter)pronounced ‘whisper’, I’ve had the program for quite a while but never really dedicated any time to setting it up, other rather checking that I can connect to the Kenwood and it allows the program to receive and transmit.

I set WSPR to report on the 30m band with a spot receiving frequency of 10.138.70MHz USB with a 2 minute RX/TX cycle using 10 Watts, unbelievably my very first report back was from the USA, this is a screen grab after a couple of hours:

WSPR on 10w
Map showing stations who received my 10 Watt transmission

Maybe my inverted ‘L’ isn’t as bad as thought! I’ll keep it running for a while and see who else can hear me. I will add to this post with more screen grabs when it has been running for longer and I get some even further contacts hopefully.

The screen shot below was taken on the 20th May 2017, I was running a Kenwood TS-200- at 5watts :

 

wspr

Advanced Exam – Update

I sat the Advanced Amateur Radio exam on the 8 December, the venue was Cauis (pronounced Key’s) College in Cambridge city center with the exam starting at 19:00, Martin from Cambridge University Wireless Club (CUW) arranged the venue and invigilated, Colin from Cambridge and District Amateur Radio Club acted as the second invigilator.

The exam had an allocated time of two hours and three in total taking the exam, the results are due 6 working days after receipt of the completed papers at RSGB Headquarters in Bedford, so I’m hoping to hear one way or the other by Tuesday 16 December using the OFCOM licensing web portal as I’m told this is where you find out earlier than wait for the results letter, the downside is that if your registration code used on the OFCOM site does not allow you past the application stage, then it may not be good news :-(.

Watch this space and I’ll post up as soon as I know.

17 December 14 – Well it’s good news, checked the OFCOM web site and bingo, passed the advanced, my new call sign is M0HTA, when I got home the envelope containing the certificate was waiting for me, posted on the 16th.

In my blog I’ve mentioned Hamtests and QADV being used as part of my pre exam revision, here are a couple of screen shots of what I did:

Hamtests

hamtestSet of 10 test questions with a 10 minute time limit.

hamtest1Set of 62 test questions with a 2 hour time limit.

The results dropped on the 7th December as my exam was on the 8th and I was panicking!

QADV

QADV resultsCombined results of QADV.

Sorry for the compressed image – the last version used was downloaded on the 6th December, 2 days before the exam.

QADV I found to be very well supported in regard to upgrades and it was very easy to use,  the screen grabs were from my Laptop, the program was also installed on my desktop so the number of tests actually undertaken is a lot higher than shown (each version change wipes your previous results)!

Many thanks to the providers of Hamtests, QADV, advice from members of CDARC and CUW for facilitating the exam.

Ham Radio Page

Made a few changes to the Ham Radio pages, this is a page that will continue to be under constant development, their are stacks of web sites dedicated to the topic and I’m refining mine to attract a general interest in the subject and a quick entry feature for hams to get search and discovery information.

If their is anything specific that you would like considering fro insertion in this page, please drop me a line using the contact form.

High Altitude Balloon Tracking

Finally managed to download dl-fldigi, this is a modification to the existing Fldigi in that it will download the configuration files needed for the balloons and upload the tracking details once received to a tracker site. so you can visually monitor the balloon progress.

The trouble I was having in downloading the program was due to my Nortons Anti-Virus not taking a liking to the download and rejecting it, after confirming that it was possible to download – thanks David, I set a restore point on my PC, inhibited the anti-virus program, and bingo, it downloaded, once unzipped and installed, I re-enabled the anti-virus and ran a scan just to make sure everything was ok, which it was.

Can’t wait to track a balloon now to see it in action, roll on Mark’s (M6CKD) next effort!

Blitzortung Build

I run a weather station incorporating amongst other things, two forms of lightning detection, the first is a Blitzortung and is based on a self build kit, details can be found on my weather site here, if you follow the build link on that page, there is further details on its construction or clicking here will take you to the build page directly.

The second lightning detector is a LD-250, the display page is here, this page allows you to set your own local lightning alert, click on the ‘User Options’ contained within the map frame to set your parameters, help files can be found here.