It has always been a desire of mine to make a VHF transceiver, something which I have noticed that there is a dearth of such projects for the amateur constructor.
Ten-Tec have a reputation of builders of fine HF radios, I should know I now have three! Since the introduction of the European Community "CE" Electrical Certification, Ten- Tec have withdrawn completely from the European market, however thanks to the efforts of the Radio Society of Great Britain, RSGB, exemptions have been made for the supply of kits. This exemption has allowed me to add another Ten-Tec to my "collection" and fulfil an ambition to make a VHF transceiver.
The T-KIT Model 1220 2 metre FM Transceiver is a PIC microprocessor controlled radio with 15 memories, built-in CTCSS and capable of power outputs of one and five Watts The addition of the model 1222 RF amplifier increases the power output to five and 35 Watts.
One of the things that I judge a kit by is the standard of the instructions and the PCB and this kit is certainly not failing in those directions. The book of words is substantial, running into a hundred or so pages, with sections for reference, assembly and service. The book of words has to be read thoroughly before hand, though I have to admit it was a tedious job at times, especially since I was eager to get started on the assembly. Another very tedious job that has to be done, is sorting through all the components and checking that they have been correctly supplied. I have to admit to skipping this stage, which in retrospect was not a clever thing to do. A vital header socket was missing and the wrong value of capacitor was supplied. Fortunately I was able to obtain these parts in the UK. Included with the manual was a large circuit diagram and board placement shadow drawing, an errata sheet and a handy reference guide printed on stiff paper. The other item of high quality was the PCB; the double sided circuit board with through plated holes was very well made, with a high degree of silk screen printing on the top side.
The assembly is sub-divided into eight phases, with a test phase at the end of each construction section. Testing was accomplished with the use of basic shack tools; trimmers, a short-wave receiver, a 2m VHF FM transceiver and a DMM. The use of a frequency counter was well recommended when setting up the receiver section, as I found it difficult to align the receiver by ear.
Each of the Assembly Phases has its own component placement and circuit drawings with double check-boxes against each section. I found it very helpful to read over each phase before starting as there are one or two tricky assembly stages. This is definitely not a "fifteen minute kit" each phase took between one and two hours, I estimate that there is at least eighteen hours assembly time, which for me was spread over a week or two, depending on my shift commitments.
Due to a mistake on my part, I managed to insert the wrong value of resistor into the supply for the display driver i/c, this and a faulty PLL synthesiser i/c meant a lot of fault- finding time. I have to sing the praises of T-KIT, they were very understanding with me as I had originally thought the PIC microprocessor was not waking up from a "sleep-mode", they supplied a replacement chip and a replacement PLL synth. free of charge, which considering the distance and the costs involved I appreciate very much.
It is refreshing to deal with Ten-Tec, which strikes me as a radio company which has not lost sight of their roots. Even the Warranty section was straight forward and almost down- right friendly. It is interesting to note one of the conditions of the warranty, which I have not seen before in any of the kits that I have built. Specific mention is made against the use of acid flux solder, using this solder invalidates the warranty.
Ten-Tec state that this kit is suitable for construction "build able" for the average amateur, though I would caution a novice or an inexperienced home-constructor to have the assistance of an "Elmer" at hand as the going can get rough at times.
The winding of coils is something that is a source of problems in many kits. the ferrite coils were all supplied pre-wound which was a good point and the coils that did need to be wound were formed over a screw thread with instructions as to exactly what was required from the winding, "looking at the coil from the top you should see five complete turns" rather than say wind five turns and leave it to the constructor to figure out what is really required. Another plus in my book.
I mentioned earlier that there is an optional RF Power Amplifier, the T-Kit Model 1222. I took-up this option deciding to get all the construction over and done with at the one time. This was fortunate, as it provided some work in the periods when I was awaiting the delivery of the integrated circuits. The 35W class C amplifier went together easily, the book of words was written in the same style as the model 1220 Transceiver. Testing is not really made until the amplifier is incorporated, finally into the main Transceiver. This RF amplifier can be utilised for other VHF radios, and could give a welcome boost to Handy Talkies, which is something I may do to my Yaesu FT23R at a later date.
Both these kits are complete, down to the last nut and bolt, so no scrounging and sourcing of components is required, which is something I revel in. A project is not really a true amateur radio project unless at least one component is scrounged from a fellow amateur!
The front panel controls are Spartan and functional; three rotary controls and four push- buttons. I have to say that I am worried about the rotary BCD tuning switch, it strikes me as being flimsy, having too much radial play and may not stand the test of time. The 15 memories are functional, with the provision for five memories with custom split frequencies.
The rear panel, has a SO-239 aerial socket, and sockets for an extension speaker and a data "packet" operation. The real panel is dominated by the heat-sink for the 35 Watt amplifier.
On air I have received reports that the mic-gain is set too low, after years of training myself to get the mic. away from my face I find it difficult to get the fist mic. close to my mouth and start shouting, SSB style! I am considering fitting a VOGAD amplifier to the kit to compensate for this, or altering the value of the mic. amplifier feed-back resistor. Something else and this is unique to the UK is the necessity to fit a 1750 Hz tone-burst generator. (The repeaters in the UK must have the 1750Hz tone to open-up the repeaters, CTCSS is a luxury. The repeater group that I belong to has eight repeaters and only one has CTCSS fitted, this will change as the development of a new generation of control logic progresses.)
I enjoyed building the kits, even when things were going wrong. At the end of the day I could have spent my money on a second-hand Japanese "black-box" and probably got a lot more "bells and whistles" for my money. This is a sad fact of home construction, when it is easier (and cheaper) to buy a "black-box" than it is to make ones own radio-gear, however nothing can replace the euphoria of seeing the kit suddenly burst into life before ones eyes.
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