AmateurRadio.com

With W1AW practically in my back yard, I get to play with some expensive toys.  I volunteer there from time to time….. and really get to play with some toys!  One thing I’ve learned (and try to teach new hams in my classes) is….. spend more time listening than transmitting!

So, on all my non homebrewed rigs, I have spent tons of time learning how to use, or installing filters and figuring out not only how they work, but how they truly help me on the air.  Software defined radio has also shown me some really neat things that can be done just playing with bandwidth and CW (especially trying to work a DXpedition!).

To that end, I finally got to play with a few switched capacitive audio filters that really had me thinking, why do I not have one!

Today I’m going to show you a few projects that can get you going.  First, the image on the right is from the NEQRP Club and their NESCAF project.  The theory of operation, I’ll quote from their website: http://newenglandqrp.org/nescaf

The integrated circuit at the heart of the NESCaf is made up of two CMOS active filters. These filters are extremely configurable (low pass, band pass, notch etc).

We have chosen to set up both filters as Butterworth band pass filters and to cascade the filters. Butterworth filters have the characteristic of constant amplitude in the band pass region, while the cutoff knee is not be as sharp as if the filter were configured as a Chebychev. We considered this an acceptable tradeoff, wanting constant volume out regardless of the bandwidth or center frequency setting of the filter.

There are two on-board trimmer pots. One is used to “calibrate” the center frequency pot. This allows you to adjust the frequency at which the center detent occurs. If you are using a rig with a transmit offset and sidetone of say, 700 Hz, you can use this trimmer to make that the center-detent frequency. The other on-board trimmer adjusts the audio level into the filters output amp. Using this pot, you can set the overall gain of the filter. This can be used to set the filter for unity gain, if desired. This way, the filter could be switched in and out, and still maintain a comparable volume level in the headphones.

Pretty neat!  This is a relatively simple kit that the club has been offering for quite awhile.  Out of stock now, but will be available again soon and priced really inexpensively – under $35.00.  If you want, all the information is available int he schematic and documentation if you want to “roll your own”.

There are some commercial offerings as well, many we have seen advertised like the one from Idiom Press (http://www.idiompress.com/scaf-1.html).  This one works VERY well, and comes as a complete kit with an enclosure.  There is some good information on the Idiom Press site that shows the response curve as well as why the filter doesn’t use DSP.  This kit is a bit more, but has an extremely high quality/professional looking enclosure and sells for $89.95.  I can’t afford one now, but when I can, I plan to build one and post details here with audio files (there is an audio file that can be played on their website to demonstrate the audio characteristics).

Here is a great video of NG9D’s build of the SCAF-1:

But, I don’t want to make this just a CW project…… how about AM?

Stewart (“Stu”) Personick, AB2EZ is a ham that wanted to work a bit on his transmitted and received audio.  He took the SCAF-1 and modified it in true ham spirit.  From his online writeup of the project:

My original objective was to demonstrate, to the AM community, the use of a switched capacitor filter for “brick-wall” bandlimiting of the output of an AM audio chain… in order to limit the bandwidth of the r.f. output signal produced by a vintage high-level-modulated vacuum tube transmitter, or a modern FET-based “Class E” transmitter.

What’s really neat, is this is a relatively easy mod to build in and expand the already excellent capabilities of a great kit/filter!  You can find full details of this modification at:  http://mysite.verizon.net/sdp2/id14.html I think the Idiom Press site has copied this info on their site as well.

A little more research on the topic led me to “An Adjustable Audio Filter System for the Receiver” by Lloyd Butler VK5BR (Originally Published in Amateur Radio, March 1995).

This is also a “roll your own” project, but gives some detail on the use of the filter in CW, RTTY, voice and other narrow bands.  This article was originally published 15 years ago and is still VERY relevant today.

I took a look at the schematic and it’s not entirely too difficult to build this in an evening or two and looks like a very useful and educational shack accessory.

You can find the article and schematic at: http://www.qsl.net/vk5br/SwCapFilter.htm

Hopefully this will whet your appetite and make you want to fire up your soldering iron and build a useful filter for your operating needs.  I know after using a few of these filters I’m left to wonder, “how did I NOT learn about switched capacitive audio filters!”.

… for making the power connector for the FT-817 a nonstandard and apparently unique size. I sacrificed the power cable of a multi-voltage wall-wart which had a set of interchangeable tips to make a cable I could use to run the ‘817 from my lab bench supply for an experiment. One of the tips looked to my eyes exactly the same as the one on the Yaesu charger, even down to having a yellow plastic insulator at the tip. But stupid me I didn’t think to check it would actually go in before severing the cable from the wall-wart and now I find that it doesn’t. So not only did the wall-wart lose its cable in vain but I now can’t do my experiement, since it would have taken longer than the ‘817’s woefully inadequate batteries would permit. Grrr!!

I can’t even find an FT-817 power cable on eBay.

Two exciting new possibilities for portable HF have become available.

Steve Weber KD1JV's ATS-4

A few hours ago Steve Weber KD1JV announced that the ATS-4 kit was available again. These apparently sell out very quickly – so if you’re interested, act now!

Many people hanging around the AT_Sprint Yahoo group have been waiting patiently for many weeks for this morning’s announcement.

The ATS-4 is a “miniature 5 band CW rig with digital mode capabilities” designed for 80, 40, 30, 20 and 17 or 15 meter operation in the field. The AT stands for Appalachian Trail. It’s tiny – according to the KD1JV site, about 1/3 larger than an Altoids tin – the universal QRP standard of enclosure measurement – at 4.9″ wide, 2.7″ deep and 1″ tall.

ATS-4 features include a built-in Iambic A or B mode keyer with three message memories. The rig can convert Morse input via paddle to transmit as PSK31. And PSK31 and RTTY are possible using Pocketdigi software on a PC, laptop, netbook or PDA.

The other exciting portable possibility – which was designed to be independent of this kind of hardware – is the SDR Cube. George Heron, N2APB and Juha Niinikoski, OH2NLT developed this self-contained and portable SDR Transceiver using a Softrock front end and embedded Digital Signal Processing. One of the features of this design is that no PC is required. This follows naturally from George N2APB’s work developing the NUE-PSK modem which liberates portable PSK31 & RTTY ops from lugging along a laptop.

The SDR Cube

The SDR Cube is still available for ‘early-bird’ special prices, so again, not one to put off considering for too long. It’s also available in a range of different forms, from bare PC boards through to kits and assembled and tested. The design is deliberately open and flexible to accommodate experimentation. As the comprehensive SDR Cube site explains

The SDR Cube is a totally self-contained, embedded SDR transceiver for CW & SSB using a Softrock for the RF front end and a pc board implementation of an HF modem.  A PC is not needed for using the SDR Cube, as all DSP processing is accomplished by an embedded DSP processor on the three internal pc boards.  The Cube is designed to fit into an optional 4” x 4” x 4” pre-cut black powder-coated aluminum enclosure containing all controls, a blue graphic display showing the transceiver settings and an exciting 8 kHz-wide band scope of spectrum signals, and the popular Softrock RXTX v6.3 board.

Full ordering details for the SDR Cube can be found here.

Today was one of those perfect days you sometimes get in winter. It was too good to stay indoors, especially as rain is forecast for tomorrow, so after lunch I packed my APRS tracker and Motorola GP300 in my rucksack and went for a short hike up Binsey, one of the Wainwright hills in the northern Lake District.

There had been a frost overnight and even now in the early afternoon the temperature was only a degree or two above freezing. Looking towards the central Lake District across Bassenthwaite Lake you could see the distant hills were covered with a light dusting of snow.

On the way up to the summit of Binsey I observed that my tracker was not transmitting. The tiny red LED on the GPS was flashing to say the receiver was working but the GPS OK light on the tracker itself was out. If I switched the unit off and then on it would send its position as soon as GPS lock was obtained, but that was usually all I got. When the beacon was sent I also heard a few noises from the Motorola receiver. None of this had happened during testing in the shack, but a cold fell-top is not the ideal place for troubleshooting. The lack of position reports received during my walk on Sunday was probably not due to conditions

On my descent I enjoyed the view of the snow-dusted Skiddaw range against an almost cloudless blue sky. To think, some people are stuck in an office on a day like this! (OK, I know, I don’t have to rub it in!)

Back home I connected up my tracker on the bench and it worked perfectly again. I then put it in my rucksack as it had been while I was out and it started to behave as it had while I was out. Some braaps were accompanied by a sort of farting sound that was probably RF feedback. I’m pretty sure RF is getting in somewhere and causing the tracker board to misbehave, but the question is: where?

I’ve tried moving cables about and clipping ferrites on the leads but so far I’m not sure what is the cause. I hate this kind of problem which can have you going round in circles thinking you’ve fixed it and then it recurs. I’m not sure yet if the RF is being picked up on one of the cables – both the PS/2 GPS cable and the curly Motorola cable are quite long for this application – or whether it is getting to the module directly since it is only in a plastic case. Perhaps I should try it in a die cast box. Any ideas?

Not had a chance to write things up since the weekend. But I had quite a varied and interesting time on the air at the weekend. Didn’t spend too much time, as is often the case, but it was proof that a few quick visits to the radio can be interesting.

First interesting contact was from the mobile, as I was driving to get some catfood on Saturday morning. I had the FT8900 scanning and as it went through GB3RD, it stopped and I heard ‘Golf Eight Delta Delta’ in a very distinctive voice and then the rig resumed scanning. I recognised the voice and went back to GB3RD. As I’d thought it was Peter, G8DDY from the Isle of Wight, who was mobile on one of the highspots of the island. I remembered Peter as being my first QSO from the Isle of Wight on both 144 and 432MHz way back in the early 1980s.

By the time I’d got the rig back on GB3RD, Peter was already in QSO, but I listened and waited for the QSO to end. It did and I called in. It was fun to speak to Peter and compare notes of operating from the island. He knew the apartments where we have stayed and how good a radio spot it is! A lovely QSO and nice to catch up again after all this time.

The first weekend of November is always the Marconi Memorial CW contest on 144MHz. Though I don’t treat it as a contest, I always tune around as it’s interesting to see what can be heard. This year was no exception and there were some nice contacts to be made. Conditions weren’t brilliant, but I was pleased to make some reasonable contacts – mostly from Continental Europe. The best DX was F8DGY in JN18. The two gotaways, at greater distance were DK0BN (JN39) heard for a reasonable period on Saturday afternoon, just above the noise and TM0W (JN36) again, heard for a good period on Saturday evening, but not QUITE strong enough to work! I did hear TM0W again briefly on Sunday, but conditions were poorer and tropo was very weak by this time (there were some good MS bursts though!).

The other experiment was to listen for the AO-51 satellite (repeater in the sky). I was inspired to do this, after seeing a tweet from Paul, 2E0BHA. I’d hoped to try and work him. However, the experiment was only partially successful in that I heard signals on the IC-E92 handheld. But despite the overhead pass, signals were weak. After the event, I discovered that the satellite had not been operating at full strength, so I shall have to try again on a more auspicious occasion.

Welcome once again to my humble QTH:

Retirement!

To many of my friends, retirement means being more active than ever and being involved in more things than while they were in the work force. Some of my other friends just sit around all day with nothing to do except watch TV, listen to the radio, or read. For me it has been a little of both. I am hunting for another job just for something to do to keep active with people on a more daily basis. Also, I have been meeting with several of the people I went to high school and grade school with so very long ago. We are planning a 70 year, weeklong, Birthday Bash because we will all turn 70 at the same time, plus or minus a couple months. Many will be flying in from all over the world. Once a month we have a lunch for those who happen to be in town at that time.

Because of my interest in Amateur Radio Since 1956, when I first became licensed, I have never been lacking any friends and have always had something to keep my interest. There is always new technology to keep up with. In fact, I have attended several local ham radio events and do a considerable amount of listening both on and off the ham bands. I also check out many of the ham radio web sites to see what is new and what various clubs are doing. Of course I have been checking out the Handiham web pages too. I have been out to the new offices and visited with Pat and Nancy a few times too. Pat & I have worked on a couple Handiham projects as well.

Which brings me to this: Although my rigs consist of a Yaesu FT-100 & VX7R , a Kenwood TS-50 with the automatic antenna tuner, an Icom IC-T7H HT, I also have and use a couple of HT scanners , a Bearcat R4020 and a Radio Shack Pro-96, which I use to listen to many things both on and off the ham bands. They scan pretty fast so I do not miss very much and I catch most of the VHF/UHF nets and things going on. Many times I am listening to the Handiham net on the scanner and go to jump in only to notice that there is no push to talk switch on the scanner.

One subject of interest to me is the question of a 75/80 meter Handiham net and where on the band to have it.

My suggestion was, half kidding, to have a slow speed Handiham CW net on 75 meters.

How about it? What do you think?

I would volunteer to be ONE of the net controls if we have some others that would help.

I know, I know… The requirement for CW has been dropped. But here is the funny thing about that. More and more people are learning the code just for the fun of it. And, some people cheat using computers to translate the code so they don’t even need to know it. If you think about it, there is plenty of room in the CW part of the band for a net and the range would be greater using CW than on SSB so people from outer areas would have a better chance of checking in.

And, Yes! I know Handihams has a Slow Speed CW net on 7112 Friday Mornings. However Paul, the net control, is on the East Coast and as many times as I have tried to check in from Minnesota no one has heard me. Another slow speed Handiham CW net for those of us on “THIS” side of the Appalachian Mountains might be what is needed.

What do you think? Please send your ideas , suggestions, wishes to be a volunteer CW net control, etc. to Pat at [email protected] and he will pass on the information to me.

So, until next time…

73 es DX de K0HLA Avery

I popped up to the shack after watching some evening TV and decided to have a listen to what was happening on JT65A on 40m. I tuned my K3 to 7.076MHz and had only been listening for a couple of minutes when I saw a CQ call from VK6BN appear on the screen. I only just managed to set up a reply before the start of the transmit period and you could have knocked me down with a feather when he came back with a report! We completed the QSO in the minimum 6 minutes.

I’ve been reported in VK before using WSPR, that’s nothing unusual, but this is my first ever two-way contact with Australia on any band or mode and I’m pretty amazed to have achieved it on 40m of all bands using just 30 watts to my attic dipole. JT65A really is amazing!

As if that wasn’t enough, I then worked KE1AF for my first contact with North America on 40m. So I shall be going to bed this evening feeling pretty pleased!