I started in amateur radio with Baofeng UV-5R for listening in February 2013, took the exam in March and then got licensed April of the same year. I enjoy using a mix of commercial 'big-brand' equipment, novelties from China and a certain amount of homebrew.
I'm currently operating Yaesu FT-817ND through MFJ-971, a KL-400 linear, a lowpass filter and antenna tuner to a half size ('Junior' / 'Mini') G5RV. I'm on SSB phone & PSK31. The antenna peak currently only at ~6m. I made and fitted a DH8BQA BX-814 'Voice Keyer' kit to save my voice when calling CQ - I'm delighted with it.
The linear I'm using is a RM Italy KL-400 for which I have made a LP output filter for 20m. I see these linears as a 'component' rather than a 'product'. Whilst the manufacturer's web page says 400W and 3-30MHz, in reality it's a 14-30MHz 150W amplifier. You must add a fan in all circumstances and also add external low pass filter(s) to use on anything other than 10m & 11m. It's an inexpensive way to go QRO from an FT-817. Here's my 20m low-pass filter enclosure - hewn from solid 100x100mm extruded 6000 series alloy bar stock. At 1.3kg it weighs more than the radio, I believe.
I made air-core inductors with 1mm enamelled wire (not a great idea, they spring about alot and so the inductance value is vague, at best), some silver mica caps and manhattan construction. Here's the circuit for 20m:
The VOX activation of the linear by 5W output from the FT-817 works as long as you don't pause for breath. With less than 5W input the VOX operation is unusable. It would be handy to be able to reduce the input power to the linear to scale back to 20-50W, but this will mean adapting the KL-400 to accept a PTT input from the FT-817 ACC interface. I got some tips from Bert van Lelieveld PA3EKA (with the help of the Wayabck Machine since his ham web pages went down some years ago) and compared his RM Italy KL-500 information with the KL-400 schematic. I hope Bert doesn't mind, here's his photo of his KL-500 Rev 3.00 mod with a phono socket to the back of the amp:
In essence, there's an NPN transistor that's used to switch the power amp side of the circuit via a relay. If you short the collector of that transistor to 0V that switches you to transmit mode. In the case of the KL-500 version 3.00 board that's TR3. In the case of my KL-400 Rev 4.10 board, that's T4, a BC547. Pull point marked with the red dot below to 0V with the PTT output from the FT-817 and then you can forget about VOX feature and switch the SSB / AM switch to AM. I did this mod by adding a wire to the pad for R23 (green dot) which is a no-fit and also connected to the collector of T4. It works just fine. While I was at it I also added a 13.8V out switched from the main amp power switch to switch the external fan. To finish, I'd like to make an isolation circuit for the PTT output. It's not that I don't trust RM Italy not to fry my precious Yaesu radio but, frankly, I want a relay in the link.
I use a homebrew, fully-isolated digital modes interface with its own USB interface. It's based on KK7UQ's design, but I use the 1kHz right channel PTT tone detected with my own circuit. Therefore only a USB sound card is needed (no serial interface). Below I've added a picture of the innards of the finished interface. You can see the 'sound card' on the right - about the size of a postage stamp after throwing away the plastics and desoldering the USB connector. The sound interface was about $1.50 direct from China including postage, not really worth making your own! The most 'expensive' parts were the isolation transformers which were about $5 each. The whole thing cost about $30 including cable, case, etc. - and I have a load of extra parts for other projects.
Here's the PTT circuit made with cheap discrete components - I was thinking about using LM567 tone detector chip but it was overkill and I didn't have any in stock:
I'm not wildly enthusiastic about the G5RV mini; I don't know whether it's because I have it in inverted 'V', but performance on anything other than 20m is not good - high SWR that in some bands I can't tune out with my manual MFJ tuner and weak signals in general. On 20m it performs just about the same as a simple wire 20m inverted 'V' dipole - which isn't surprising. Although at the 20m PSK31 frequency, 14.070MHz, I can't tune to much better than 2.0:1 when on the KL-400 (wound down to below 30W). All in all, not that great. I have high hopes for the Moxon.
Homebrew projects underway: a tapped-coil loaded multiband vertical for portable use with a fishing rod, a VK3YE-style magnetic loop, a PTT interface for the RM Italy KL-400 linear and a multi-band hexbeam or Moxon antenna.
My 'lab' is equipped with a linear 0-30V, 2A linear supply, a 45A 13.8V switchmode supply, an Owon DS7102V scope (much maligned, about a million times better than no scope at all), some cheapo multimeters, a SARK-100 antenna analyser clone ('Mini-60') which works very well, usual handtools, breadboards, etc. and benchtop bandsaw, lathe + mill.
I tried a VK3YE/Par End Fedz 10/20/40 antenna for portable but I can't get SWR better than 2.5:1 on 20m so I need to rebuild using the toroid that VK3YE specified and also pay attention to phase of input and output coils - it may not be a scapper yet.
QSO's as of 15 Sep 2013:
I received my first ever QSL cards printed by LZ3HI on 3 Sep 2013. Currently I have no bureau - I prefer LoTW but will also QSL direct. Here's the artwork for the QSL cards.
Finally, if you speak Spanish, please have a look on my pages at RadioClub San Javier.
Last modified: 2014-02-22 20:42:14, 6642 bytes
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