CB testing

I recently constructed a dummy load, using instructions I found on the Internet, that consists of nothing more than salt water, a container, a SO239 in top of container, some silicone sealant, and two pieces of copper wire (Google search for "salt water dummy load" if you're interested and want to make this yourself), because it contains salt water and a large amount of RF will heat it up, it makes it perfect for use on legal CB radios that output at 4 watts, at the moment it is connected to my Midland 78 Plus Multi B, though I plan to swap it to my Moonraker FA5000 as I reserved the Midland for car use.

The primary reason for connecting it up is because I had built it some weeks ago and had initially calibrated it on the Midland, and after that it had been stood for some time so I was not sure if it was still working as it did when I built it.  I do own a Zetagi DL50 dummy load that can take 50 watts but reserve this for serious rig testing (for example if I suspect the finals have blown in a CB), this saltwater load, which I keep connected to a spare SWR meter, is for using the rigs short range, for example testing the received audio on the Free Radio Network CB gateway, as I suspect right now that it is a bit over the top on some rigs, it appeared to be on my Midland 78 so I will look into dropping the volume down a touch, the test room parrot may be of some help here, thus the secondary reason for connecting it to a radio.

I have to go to conduct the remaining audio tests on the gateway, as well as other things, so will return soon with more of my goings on in the world of hobby radio

73 de 26CT730

Updates

I have not been able to update this in a while as I have been very busy, not been able to get on air much either but that should be set to change.

The CB gateway is now operational part-time, I managed to get an antenna up in the loft, an "excalibur" antenna which is the smallest antenna I could find and the only one that would fit in there, though still had some SWR issues so have had to use a matcher as a stop-gap, but I can hear it on a handheld at least two miles away on it's rubber duck antenna so it must be getting out fine, it's times of operation, though not totally set in stone, are 9am-5pm Monday to Saturday, it may not operate on Sundays, and we're almost into week three with it.

I have yet to achieve my Amateur radio foundation license but I hope to get that this year if all works out well, and GB3IR, the local 2m repeater, is still operating, something I sometimes listen to either on my Wouxun handheld or the RTLSDR though that is currently purposed for something else right now.

Once I got the RTLSDR going properly I was able to receive APRS, pagers (which surprised me), ADS-B at 1090MHz, GSM phones (though for obvious reasons I was not able to decode them), the television band (which is solely occupied by DVB-T and DVB-T2 transmissions), some VHF business band transmissions, PMR446 (including the Richmond PMR446 FRN gateway which of course is in the same room), the broadcast band, the airband, and a radio controller for a novelty inflatable robot that operates somewhere in 49MHz (I think) and interestingly using AM to carry both voice and it's data packets to control the toy it goes with, I was not successful in receiving any CB traffic though the tuner can tune down there, even to 27.555MHz.

I have also put together a salt water dummy load from instructions I found on the Internet as I had all the parts required and it works reasonably well, not perfect but I only need it to dump RF into if there is no antenna rather than test power output which is what my manufactured dummy load is for.

I also discovered another issue with radio's public enemy number one, PLT adaptors, it has been found that these things not only wipe out radio spectrum but they also have the potential to connect to other houses in the same street, there's evidence on the Internet of this where BT Internet customers have found their connection suddenly change to TalkTalk, which without the PLT devices is not possible because the BT Home Hub cannot authenticate to TalkTalk's systems, so a massive security hole there, perhaps less of these things will be in operation now for fear of other people connecting to them and "stealing" internet.

I'll try and update more often and I should be back on the air properly soon

73 de 26CT730

SDR in the shack

The RTLSDR device arrived this morning and I have it currently in the shack connected to the shack computer, when I have a bit more time I will play with it further, perhaps even on my Android phone as I hear with a USB OTG cable this is possible.

I shall let you know how I get on

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Software Defined Radio

I am adding Software Defined Radio to the shack, this is in the form of a Realtek RTL2382U based USB DVB receiver, equipped with a R820T tuner that can receive from 24MHz and up, the shack computer has been set up in order to be able to utilise the RTLSDR when it arrives.

The receiver in question is this device from Amazon.co.uk.  The device comes with a very short antenna that plugs onto the unit using an MCX connector so you will need an adaptor to the Belling-Lee connector, then if you want a reasonably better connection you can get an adaptor from Belling-Lee to F connector

As a stopgap you could use a pair of "rabbit ears", which you can get from Poundland in the UK (or whatever you have in your country that is similar), something I have actually done with the FM broadcast receiver in my living room's Hi-Fi system and it works well in Band II despite suffering some damage, though it should receive other frequencies but a better antenna and coaxial cable would be more beneficial when possible, especially an outdoor antenna as it would be less prone to interference.

The same coaxial cable used for satellite dish LNB feedline is also a good idea as that is low-loss.  There are instructions online on how to build antennas for use with these devices as well as suitable software for all platforms and the drivers to make the devices work, do not use the CD supplied with the device as this is the software for using it as a television device.

This is something I have been meaning to play with for a long time, now I have that opportunity to do so, stay tuned for more.

73 de 26CT730

Scooter CB... the theory

I plan to purchase a 50cc scooter/moped in the not too distant future as I am starting to find bus fares are costly and am spending £15 a week and I'd spend less than that on riding a scooter a week, and I plan to fit it with a CB radio.  I have identified a few issues already that have to be overcome, these are:

1. Lack of a suitable groundplane, without which a standard mobile antenna will not work, so an antenna designed to be fit to fibreglass vehicles would be needed, at least two have been identified as suitable though it is possible to buy an EGP kit, however I cannot buy this until I have the scooter.
2. A suitable power source.  My understanding is that most modern scooters have a 12 volt electrical system, so simply fitting a cigarette lighter socket to it should be no problem, this will then accommodate the car adaptor supplied with current handheld CBs such as the Intek H-520 and Midland Alan 42 Multi (I have both radios and bought the latter specifically for this).  The supply would also be fused on the socket's positive line to avoid any fires or other such issues, and possibly ignition-switched
3. Headset.  A standard CB radio cannot accept an Icom type headset connection (as found on PMR446), except on some very expensive radios that putting onto a scooter would not be wise to do and would not be removable as readily.  As all handhelds currently on the market are Icom headset compatible this makes them usable with motorcycle headsets which simply are fitted in the rider's helmet and have a PTT on the handlebar to allow transmission, handheld CBs do not have VOX either so this may be solved already but I need a motorcycle helmet first.
4. Mounting the radio.  This will depend on the scooter, the handlebars themselves are a no-no for obvious reasons, it would need to be mounted so it can be accessed easily yet not interfere with my operation of the scooter, the planned mounting location may also dictate the location of the cigarette lighter though I may use the same socket to charge my mobile phone.
5. Ease of removal.  I decided that the Intek H-520 Plus is quite a cumbersome radio for this task, as is the cheaper H-512 as it uses the same basic case, so instead I chose the Midland Alan 42 Multi. Also the car kit supplied with the Midland slides onto it in place of the battery box, the Intek radios use a small screw to hold it's car kit in place on the underneath of the radio and requires the user to remove one of the batteries before using it on a cigar lighter socket.
6. Waterproofing.  The antenna connection can be waterproofed with self-amalgamating tape, in particular the connection at the antenna itself as this will be permanently connected, the radio itself however is something I will have to look at at install time.
7. Security, as the radio is quick to remove this should be no problem, when I am not using the scooter I simply remove the radio and return it to the house.

I am not the first person to fit a CB radio to a scooter/moped, I know of at least one other that has done this, though they used a different radio, a Midland 38, I suspect this was for static mobile use rather than actually on the move given the radio used.

I will post an update once I have a scooter and put this theory into reality. I will also include photos of the installation.

73 de 26CT730

Another 446 gateway update

It has been a while since I've been able to get on air as the last few months have been VERY busy for a variety of reasons.

The PMR446 gateway computer failed again but I may have solved the problem.  The current 80GB hard disk was not being detected, I have, however, replaced the power supply, which was just out of a theory I had, and the hard disk was detected and the gateway computer booted successfully, the gateway is now operating on it's usual channel and CTCSS combination, it has also been up for a week without a fault, I am keeping a reasonably close eye on it though I'd need to keep a radio on me at all times to be absolutely sure and I would not be able to do so.

I am happy that the gateway is back on air, this means I can hopefully restart work on the CB gateway again, and hopefully that will be on air before the end of the year.

73 de 26CT730

446 gateway update

I have managed to get the PMR446 gateway back on air within the last 24 hours, using the 80GB WD hard disk, the original Maxtor hard disk has completely failed and has been removed from the machine awaiting tests to find out what happened to it and if it can be salvaged.

Reconnection of the autokey device to the computer was straight forward, it worked the first time, though there is an undesirable hum in the received audio it does not have a major effect and transmissions from the gateway are perfectly audible.  I may look into fitting a ground-loop isolator onto the gateway to see if that cures it but it isn’t a major issue at this time.

The gateway is operating on it’s usual channel and CTCSS, so feel free to use it if you are in Richmond, you may not get a reply immediately but be patient.

 

73 de 26CT730