AmateurRadio.com

Screenshot of Warbler contact to Alabama

Last night I used the Warbler I finished a few months ago and had a very nice 40 minute QSO on 80m with Ken, KI3N, in Oxford Alabama.  First, it great that conditions were good enough for us to chat for 40 minutes using PSK31, but when you consider that the distance between us was about 970 miles then that made it quite an achievement given the band.  I was using the Warbler, putting out 3W now after some slight changes, and the 88ft doublet tuned with the homebrew ATU.  Ken was using 40W from an Icom IC-756 Pro into an 80m dipole.  The screenshot above shows what I was receiving.

Even though the Warbler is rockbound and uses a direct conversion receiver its performance is very good and makes it fun to use.  This was the furthest contact I have made so far with that transceiver.

When Work Gets in the Way of Ham Radio

Every now and then we hit one of those seasons of life where our work gets in the way of our hobby. For the past month, seems like work has overtaken the time and my radios have sat idle for WAY TOO LONG.

Thankfully, this weekend brings some relief and our Central Florida QRP group will take to the outdoors for our monthly outing. No one will be able to complain about the weather being too hot either, as the northland has sent us a reminder of why we moved to Florida. When it gets below 55F we get cranky and it looks like it will barely go above that temperature this weekend.

So look out for us this Saturday, 11 December 2010 about 1500-2000 UTC on the QRP watering holes on 40m, 30m, 20m and who knows where else. We’ll be out there with rusty fists on the keys once again. YAHOO!

72,

Kelly K4UPG PB #173

Calling all Central Florida QRP Ops… there’s a small group of us in Orlando that like to gather together on the 2nd Saturday of the month for some breakfast, show n tell, and portable ops in a nearby park.

Antenna Tweakers

Operating site

K3RLL in action with KX-1

We just had a nice time of antenna tweaking and operating down by Lake Sylvan. There’s still room for more of you, so mark your calendars and plan to join us on the 10th of December 2010. Leave me a comment if you’d like me to send an email reminder to join us, or if you’d like to get on our list for future outings. Snowbirds are welcome too!

72,

Kelly K4UPG PB #173

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!”.

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.

Recently I began a project for a wire vertical antenna and it called for a 20 ft fiberglass or non-conducting pole/mast of some sort. Not to worry as I have a trusty 20 ft Jackite pole in a nice green color. I put the antenna together but the vertical wire was too long and so there was considerable slack wire swinging in the breeze. After some head scratching, I measured my 20 ft Jackite and found it was only 18 ft long!!! YIKES! Did it shrink?

Did it shrink? Nope, it is all good to go!

Thanks to the internet, I was able to send an email to Jackite products and ask if that was normal. In a short time, I received a very nice response from the Jackite vp and an offer that was over the top and way more than I was expecting. It was more than I could accept as I’ve been quite happy with the product otherwise. Turns out that it was a small quality control issue that I can tweak and correct personally.

I get no monetary or other gain out of this, but did want to give credit where credit is due. This level of customer support is often lacking in today’s busy world. I am glad to give a shout out to this company and its products! They do the job and the company stands behind them with good service. Outstanding job Jackite!

72,

Kelly K4UPG PB #173

Yep, it is confirmed now for sure. Compulsive Antenna Disorder has haunted me since I was first licensed and ran a coax fed 80 meter dipole on multiple bands without a tuner.  The first time the symptoms were noticed by my family and friends was when I got a couple OO tickets for out of band harmonics. Hmmmm… what’s up with that? So a bit of reading and the antenna tweaking began and that’s when it all started.

Soon thereafter I tried to load up a nifty pin from my Junior Prom Boutonnière that reminded me of a triple stacked halo for 1296 Mc (MHz for the newer ones amongst us).  Then it was the handheld yagis for 432 Mc that we used with some military surplus gear that used dynamos so we could chase tornadoes. (We thought if it bounced off the moon, it should bounce off of a tornado!) The saucer sled that became a parabolic for listening to satellite telemetry and on it goes… Compulsive Antenna Disorder has had a firm grip on me for some time now.

Am I dreaming? Thanks wiki images!

As a QRP operator, I am always looking for more antenna power. I know that somewhere out there simply MUST be a silver bullet, that magic QRM and pileup busting antenna that makes my 2 watts output sound like a full gallon.

I can say one thing for sure, I know a lot of non-silver bullet antennas, as I have a box full of them.

But they still make a few QSO’s at times and I’m having fun along with a bit of frustration and disappointment as I deal with my CAD affliction.

I’m told that much like telegraph key collectivitis there is no known cure or relief. I share in your grief brothers and sisters…

72,

Kelly K4UPG PB #173