Filling the void

When the Bournemouth repeater GB3SC closed down the 2m band turned into something of a local backwater. Jon G7ICH, myself and others used to hold court every morning on our daily commute via SC. To say we missed it would be an understatement, but life moves on and we let it go, because people changed jobs and their priorities change; the stuff of life!

However, with the coming of the digital revolution including Fusion and DMR, it was considered that a local DMR repeater might be a nice thing to have, particularly when connected to Brand Meister. I found a site on a high point overlooking the Poole conurbation which proved to be a good spot for our 70cm box GB7DR. The repeater deck was provided by my very generous employer and fellow ham Nick Foot G4WHO (now silent key) and the infrastructure was paid for by the Poole Amateur Radio Society. The site is provided free by Alfatronix Ltd (https://www.alfatronix.com) who keep the repeater fed and watered with a smattering of internet access. Now the bugs in the intranet firewall at the site have been sorted by Jon, the repeater gives trouble free access to DMR system - give it a go.

Analogue

I'm a self-confessed analogue amateur/engineer, and I've never liked the speech quality provided by the DMR system, plus being digital you can never have a marginal contact, when the signal gets too weak it just stops trying!
Jon, myself and several other local amateurs thought we should plough on and aim to get an analogue repeater to replace GB3SC. After asking around we managed to snag a free 2m deck in the shape of a Philips/Simoco PF10. This was kindly donated by Andrew Barret G8DOR, (past) ETCC Member for the South West. We then became doubly blessed by a chance meetings with an ex-radio amateur, turned PMR engineer Gary J. Simpson (www.commsouthern.co.uk) and ex-Southern Gas communication engineer, Mark G4SDR.

Suitable Site 

At this point we decided to look for a suitable site - having lived in the Poole/Parkstone area all my life I know the topography quite well, and the location of most of the PMR repeater sites since becoming a radio amateur in the 1980s. Several locations were selected and letters were written to site owners, only one came back as a maybe and that was from a social club in Upper Parkstone - just spitting distance from a PMR site that was about to be decommissioned. We had a couple of meetings and the senior trusty of the site, a once enthusiastic SWL, found us some attic space and a outside wall to mount the antenna, roof space proved to be warm and dry and had easy access to authorised personnel.

Lock Down

The repeater ran for nearly a year, but due to lock-down rules our friendly social club didn't ride out the economic tsunami caused by the virus. So we had to remove the repeater and start again at a new site. We got permission from Nick Foot my managing director, just weeks before his demise, to set the repeater up on a old PMR mast placed on his industrial unit by a previous tenant. The repeater was given space on a storage platform in the unit and given an AC supply and access to WIFI. The site was not as well served by the local topography, but it proved adequate after the application of an low noise receive preamplifier, which then made it accessible to most mobile stations in and around the Bournemouth and Poole area. Thanks go to Alan G7NYI for providing a brand new antenna, as the previous item had proved unreliable, and to Carlo G7IRU our group antenna rigger for fettling the feeder and mast instillation.

Something Borrowed.....

Since the first instillation of the repeater, we had been given two scrap Simoco TF2000 decks by Gary Simpson, both needed repair but after some TLC from me and help from the guys at the Simoco UK service depot both were made operational. We had by the second instillation acquired support and equipment from: - Les, G0FAJ, for the antenna and bandpass filter, Paul Marsh M0EYT, Jules Smith G0NZO and Kevin Nice G7TZC for the Heliax feeder and filter cavities. As the four cavities didn't offer the required isolation needed for the industrial location, John Fell G0API provided a circulator from the original GB3SC repeater and a low-noise pre-amp. In addition we had some financial support from the membership of the Poole Amateur Radio Society G4PRS, and a good deal of technical expertise was also provided by M0EYT, G0NZO and G0API.

A Repeater Is Borne 

We were asked by the Poole Amateur Radio Society G4PRS, if we could christen the repeater with letters to denote it was the Poole repeater, the closest we could get was GB3PB - Poole Bay. So the GB3PB repeater is borne a second time, rising from the ashes of its previous existence, providing an analogue gateway linked via Allstar to the internet. However, due to security issues it was not possible to access the repeater directly from the internet, so using RF activations and the DTMF protocol described on QRZ.com entry for GB3PB, the Allstar system can be activated. In order to offer this facility, Jon G7ICH (who is now recognised as the IT expert in the group) used a PC based application to control the repeater and a Raspberry PIE to interface with the Allstar system.

Repeater Community 

Unfortunately, COVID saw the demise of my friend and long term employer Nick Foot G4WHO. Nick was a leading light in the development of amateur repeaters locally (GB3SC & GB3SZ both silent key) but his legacy lives' on in GB7DR which he purchased, and the siting of GB3PB at his old company near Wimborne. In fact without the support of all the above persons and many I have not named, GB3PB and GB7DR would not exist. The hardware of both systems is owned by the amateurs that provided it and is a testament to the term community repeater. The best complement you could pay to the memory of Nick and co, is to use our repeater and enjoy the hobby of amateur radio and mobile operating.

Repeater Details

GB7DR occupies Channel DVU34, RX-439.425MHz, TX-430.425MHz, Colour Code 5, Slot 1 - Talk Group 9 (Local QSO), Slot 2 - Talk Group 950 (Brand Meister). Located Canford Heath, Poole. Keeper is Jon G7ICH. For complete operating details see the repeater entry on the QRZ.com web pages.


GB3PB is a 2m analogue Allstar enabled repeater serving the Poole Bay conurbation and outlying areas, AllStar node 510620. Channel RV50, TX-145.625MHz, RX-145.025MHz RX, CTCSS 71.9Hz. Located in Ferndown. Keeper Jon G7ICH. For complete operating details see the repeater entry on the QRZ.com web pages.

Last go round

The repeater GB3PB gives good coverage over the Poole and Bournemouth basin with outstanding coverage to the north of Poole, despite for the height of the antenna. It does however, have a few holes in its coverage due to the nature of the local terrain. If we could get the antenna another 5 to 10m higher, then most of the issue would disappear, but the antenna is as high as our very generous landlord would permit. :)

QRP VSWR meter that actually works.

I've been searching for a simple and cheap VSWR meter circuit that doesn't use a resistive bridge. The resistive type works well but I've found them a nuisance, as they have to be switched out of circuit when not in use as they attenuate both RX and TX signals.

Just by chance I was doing a Google image search on VSWR circuits when I came across the following from PY2OHH. This design is not easy to find on the web so I thought I would share it with you here.  In most cases I only build the reveres power side of the circuit as this is the parameter I'm normally interested in. I can assure you it works very well indeed, even with a 1mA FSD meter.  However, It does tend only runs out of puff on Top Band where it requires the full 5W to get a meter indication, all the other bands up to ten meters works fine down to 1W.

I plumped for the coiled strip-line version and used a germanium point contact diode, similar to a OA81 device to get the best sensitivity. The design is simplicity itself with no complicated coupling transformers, plus its really easy to align.

The link below takes you to an English version of the design. Miguel is experiencing some issues with his web material so I've copied his design to my Google drive.

PY20HH Design on my Google Drive

Picture from PY2OHH project notes.

30MHz and Above.

Why is there a demise in analogue amateur activity on the VHF and UHF bands, digital modes such as WSPR, FT8, Fusion and DMR are not completely to blame. The release of  digital modes, to Foundation class licenses has, in my mind, caused the problem. If a 24 month period of analogue operation on bands above 30 MHz was included, with QSL proof, became a stepping stone to the next license class it would help. Exposure to the 6m, 4m and 2m band SSB and FM would have made these operators aware of the DX possibilities of these bands, and given them a life long appreciation VHF and above. As it did me as a Class B operator under the old license scheme. I often still sit on hilltops listening for summer tropo signals to appear on hot days and for Sporadic-E openings just before a good Autumn thunderstorm. They have missed all these mystical and magical phenomenon which are a delight to me even after all these years.

Eazy Hi-Z Phones

I was looking at throwing out some scrap office telephones at work but we are not able to dump electronic waste in to our refuse. So I stripped them down to recover the plastics and was left with a pile of electronics. All good stuff , Jolly Useful Necessary Kit (JUNK) - switches, electret microphone inserts, medium impedance earpieces and other goodies like piezo sounders. Seeing the sounders took me back to an article I saw a couple of years ago where an enterprising SWL had fashioned a couple of these sounders into a pair of high impedance headphones.

Now from time to time I like to build a crystal sets just to remind myself why I got interested in radio, trouble is the only devices I have for listening on is one of those uncomfortable crystal earpieces, salvaged from an old hearing aid. So I decided to build a pair of high impedance phones using a cheap pair of ear-defenders and two of the piezo sounders.

The sounders have a very high impedance, too high for normal use, so I wired a 43k Ohm resistor in parallel with each sounder and then placed a sounder each defender ear-cup. I wired them with the cable salvaged from one of the phones in the same configuration as a stereo headset, terminated in a miniature stereo jack plug. This enables the inserts to be wired in series or parallel, in parallel the impedance of 21k Ohms is just about right for crystal set use.

Any sounder can be used, from the type you may find in musical greetings cards to the old trim-phones - bigger the sounder the better the low frequency response.

I'm very pleased with the result, my new headphones are comfortable and have a nice frequency response for communication use, together with a couple of useful resonances for peaking Morse signals - particularly good when used in conjunction with one of my simple valve regen receivers.

Selection of salvaged piezo sounders

Piezo sounders installed in cup including 

original sound deadening foam behind each insert

Finished phones including salvaged curly wire

 

 

Link to original article

https://web.archive.org/web/20220406231750/http://makearadio.com/misc-stuff/piezophones.php

Modified End fed matcher

Since my original post regarding my linked end-fed half-wave antenna and matcher I've decided to extend its range to include 80m. The switch I fitted to add the 60m band was replaced with a centre off change-over type. The extra place on the switch puts a 600pF silver mica cap in parallel with the original tank circuit - 600pF is not a common value so I made it up with several devices in parallel. So with the new switch in the central position the matcher covers 40m  to 15m, first position on the switch enable the 60m band and the second the 80m. The test button that was fitted to put a 3.3k termination in place of the antenna was replaced with a toggle change over type as the original was too hard to operate with cold fingers. The 1k resistor in series with the VSWR dip indicator LED has been replaced with a 4.7k to improve the dip indication - see the accompanying circuit diagram.

Waste not want not.

I've just recently gone around the house swapping out all the 50W GU10 spot lamps for their LED equivalent. Prices on the web have dropped to well bellow £3.00 each when purchased in bulk. The only trouble is I now have a box full of partly used 50W incandescent spot lamps.  However, as I have a workshop and a little used studio, all populated with old drawing office angle-poise lamps I decided to re-cycle the lamps in these beautiful old fittings. The CFL (compact fluorescent light) spot lamps are really expensive and give a very poor light when they get old. So having dredged through several of the auction sites I came across these nifty little adapters shown below. 

I'm  now using the 50W lamps is wasting energy but throwing them away is too. However, they were used four at a time in the fittings we have in each room, 200W just to light the lounge, reusing theses lamps one at a time isn't too bad! I reckon my supply of second user lamps should see me OK for the next twenty years. These adapters are also available in ES (Edison Screw type). You could,  if the fitting allows, use them to put LED spot lamps in your favorite retro angle-poise! When looking for these adapters use the terms "BC to GU10" or "ES to GU10 adapters". 

73 Rick G6AKG

UT5JCW 4 Meter Transverter Reveiw

I was lucky enough to spend this weekend playing with an old Deecom 4m HB9CV beam antenna and as this coincided with the 4m cumulative contest I decided to give my portable station a workout. This flurry of activity was spurred on by the many thunderstorm that have triggered sporadic-E openings well into this summer. My hope is to go and activate a local SOTA site this Autumn.

My backpack station now consists of a 70MHz transverter, a fishing pole mounted HB9CV beam antenna, a Yaesu FT817ND transceiver and a homebrew 12V power pack.

Supplied transverter PCB

Serge (UT5JCW) produces transverters for bands from 50MHz right though to 430MHz and I can confirm the 4M PCB is slightly larger than a credit card, it makes use of mainly SMD components with the exception of Inductors and the PA transistor. The PCB is supplied fully aligned and produces in excess of 10W when running from my gell-cell portable power pack. After carefully adjusting the transceiver drive level I did some quick tests which proved a nice clean output on 70MHz, with a second harmonic 39dB down on the fundamental. The close in emissions noted at 84MHz (2 x the local oscillator crystal at 42MHz) were better than 40dB down on the output signal.

So after extensive bench testing, I've finished boxing up my transverter and made several successful 4M band SSB contacts using my newly acquired Yaesu FT817ND as the driver. 

Rear of supplied transverter PCB

The receive sensitivity seems similar to that of the drive transceiver on 28MHz and the only problem noted was a slight frequency skew in transversion, of plus 5.8kHz. However, I didn't view this as a deal-breaker as this can be programmed out in my home QTH transceiver and mentally accommodated when out portable .

Serge did suggest that a suitable inductor could be connected in series with the crystal to drag it on frequency, but the PC board is so neat it seemed a shame to start hacking it around. Surge commented that in order to keep the price down of the product he had used computer grade crystals that were not noted for their accuracy.

Included in my box is a variable 30dB power attenuator, as suggested by Serge in the application data, as the transverter only requires 100mW drive - maximum! I also added to my project an RF activation circuit to operate antenna changer-over relays, as the barefoot transverter PCB has no switching hardware. A separate socket was added to make use of the grounded PTT line which is available on the ACC socket of my FT817. 

My boxed transverter including power attenuator and relays, the heat sink is from a faulty industrial PC

Overall this transverter represents good value for money and since I purchased mine, Serge has added some accessories that make its application even easier - as he now offers a ready made relay and power attenuator PCB. In fact you can buy a whole kit including the case for approximately £80 - see his  Ebay Transverter Store.

Many thanks to Serge UT5JCW for his prompt help in answering my technical queries and use of his circuits diagrams and photos in this blog. 

Transverter technical specifications

• RF range  -   70 ... 72MHz
• IF range  -  28 ... 30MHz
• IF input power  -   1 ... 100mW (0.1W max.) or 0 ... 20dBm
• LO frequency  -   42 MHz
• LO frequency stability  -   +/- 3ppm
• Output power  -   10 ... 15W
• RX gain  -   typ. 20dB
• Noise figure  -   typ. 1.0dB
• Image rejection  -    typ. 70dB
• PTT control  -   Contact closure to ground
• Supply voltage  -   +13.8V DC (+12 ... 14V DC)
• Current consumption  -   typ. 2A (TX)
• TX Output transistor  -   RD16HHF1
• RX Input transistor  -   BF998
• Dimensions (mm)  -   80 x 45