I left you last having completed the installation of the vertical. I'm pleased to say, it's still up! And yes, I'm having a blast being back on the air. Here's what I've been up to.
After getting the vertical up, I set to putting the SB-200 back on the air as well. Last time I shared SB-200 stuff with you guys was when I just about killed myself by sticking my hand in the chassis with the HV power applied. I definitely learned my lesson and took many extra precautions this time around. Getting the SB-200 out of storage and converted back to 120v (no 240v in the new shack) I noticed the softkey circuit I had was not working, there was no keying action. The circuit was powered by a 3v lithium coin cell so its no surprise. I thought while I was in there, I'd rework the 12VDC power rectifier I built for the PC fans I put in there in our last blog post.
I decided to go full hog and just throw a 12v transformer, as well as cut out the case for better air flow. This turned out to work a lot better than the way I had it hooked up before and I didn't have to worry about the filament voltage from being impacted in any way. Unfortunately I did find out that you can't ground the DC side of the transformer to the case. It took a while to find out why the fan would stop when transmitting. In investigating all of that, I ended up going down to just 1 fan and I can definitely tell it works really well with just the one to keep the tubes cool.
Since I was running the amp on 120v I wondered if I could improve the performance with the lower source voltage. With the exception of the soft key and the fans, I'd made zero modifications or updates to the amp. Surprisingly the amp was totally untouched and working great all things considered. And yet, I had picked up replacement capacitors for the power supply when I bought the amp at Hamvention so I figured it was time to just replace the aged ones in the amp. You've probably seen pictures like the one below on the internet and I always thought, "oh that's a blown up cap," but it turns out that's just the glue that goes in the paper covers! All 6 of the caps in my amp, did end up being absolutely fine, but I did find a bad diode which I also replaced.
Everything else checked out and once it was all buttoned up everything looked great! I got the amp back on the air and it didn't take long until I reached the limit of the 15 amp circuit to the shack and that was about it. It became painfully obvious that I was just not going to be able to run an amp in the new shack without a more worthy circuit. And, do be honest, in all these years, I've not really enjoyed using the amp on CW. Friends will tell you, I'm a little extreme about having a quiet shack and once you get rid of the fan noise, the SB-200 is silent...until the T/R switch goes off. And man is it loud! I seriously considered adding QSK but it turns out there's no "drop in" boards available anymore so I kind of went off the deep end...
In addition to the fun at NR5M last weekend, I spent part of Sunday getting my station up and running at the new apartment. This mainly amounted to mounting and tuning my 20m hamstick and running cable to the radio. This doesn't sound like much on paper but it was a lot more engineering than that.
I started by scraping a bit of the paint off of the balcony railing as it would serve as the counterpoise for the hamstick. The bracket is held to the railing with a small clamp. Initial testing showed that it was secure enough to withstand some stormy weather. I'll probably still take the antenna off the mount if things get really windy.
I whipped out the FG-01A analyzer from YouKits and got the tuning just right but as expected, the SWR was a little high at 2:1. A well tuned, high efficiency vertical will have a fairly low feedpoint impedance and I was showing about 23 ohms. The plan was to run RG-6 (75 ohm TV coax) so that'd give me a pretty bad match at around 3:1 VSWR. The coils in these compact mobile antennas can make them look a little long so adding some shunt capacitance at the base can help bring the feedpoint up into the proper range for good SWR without sacrificing much efficiency. I grabbed my junk box caps and started trying them out while monitoring the SWR at the end of the feedline. I found that 100pF worked perfect and got me right at 50 ohms at the transmitter end of the feedline. Unfortunately all I have are little 50v caps so hopefully this one will not blow up too quickly.
Back to the coax for a bit: it isn't uncommon for hams to use 75 ohm coax since it is usually super cheap (sometimes free) and has excellent low loss characteristics. The only drawback is that it is not quite as easy to put connectors on, due mostly to the aluminum shields. I found a video on youtube though that explained a good way to put a PL-259 on it so I gave that a shot with (at least temporary) success:
Up until now, everything you've read was pretty easy. The hard part was going to be figuring out how to get the coax from the balcony to my desk, which is about 50' away. And I'm on the 3rd floor. And I don't want to just have coax hanging outside, drawing attention. Not to mention, how do I get the coax from the balcony to the window of the shack, 30' away, while I'm up 3 stories?
There were a few options. I could pull the cable through the window closest to the balcony and run it inside to the shack, but that is probably the least preferred option for obvious reasons. I could run it mostly outside but snake it in and out of the windows across the living room wall, but then the coax has to be crushed in the sill many times. Also not a very good option.
I was thinking more and more about the last option and it hit me, if I could somehow hold the coax on the sill outside the window, it would be invisible from the ground and mostly invisible from inside. I'd need some kind of hook to hold the coax against the bottom of the window but still be able to close the window.
Now, we all have times that we doubt our abilities and I have that as much as the next guy, but there are also times when you do something that makes you think "I am pretty cool!" and this happens to be one of those times luckily! I devised a way to hold the coax to the window sill without it being visible from the ground and without impeding the operation of the window: zip ties. I looped the zip tie around the coax and squished it in the window sill under the screen. This gave the zip tie enough to grip to and hold the coax in place but still small enough that it did not bother the window at all. It's best understood by this picture.
I tied off the coax across the sill 2 times on each window and it looks awesome! Here's a couple shots from the inside of the apartment and from the ground so you can see what the layman would see. It is pretty inconspicuous. I think the only way to improve the look would be to put some tall plant in the corner of the balcony to disguise the antennas a bit but I'm not sure it'll draw too much attention as-is.
Once I got everything up and running, I jumped in the WPX contest with 3 hours remaining and worked 69 guys with 65 mults in the log for just shy of 10k points. Not bad for a very casual single band operation at 100w. Plenty of DX in the log too which is great news. The balcony faces the NE so I should have a good shot to EU. I ran WSPR at 5w for a while on Monday and here's a snapshot from the day:
I'd say the antenna is working pretty well. Noise is low here, typically below S2, and as far as I know, I have not caused any interference. Win-Win! I'll keep you updated as the station continues to evolve and if any exciting DX comes in!
I'm still having a lot of fun with my new TS-590 and this week's addition to the enjoyment was the addition of an interface for producing real, in-rig frequency shift keying for RTTY rather than using a program like FLDigi to produce the tones in a sideband signal. The benefit is that you don't have to worry about audio levels or producing excess IMD and when chasing RTTY spots, you don't have to figure out where to set the receiver passband.
I ordered an FTDI USB-Serial adapter which provides 5V TTL levels which can be fed directly into the TS-590's ACC2 port for PTT and FSK. I did not know it would be that easy though. No, instead I started by building a transistor based switch that would drive outputs to ground when the RTS or TXD lines from the adapter were active. The problem is, at least on OS X, when the adapter is not being actively used by a program, the RTS line is active, meaning whenever I was not operating a digital mode, the rig was being keyed. You may think, "well on the 590 you can just change the polarity of that signal so it doesn't do that," and you'd be right, but for whatever reason, I just could not get it to work that way. Never the less, I fooled with this transistor interface for about 2 hours until I finally gave up and hooked things up directly to the adapter. Sure enough, it worked exactly as I wanted it to without any problems. We live and learn I guess!
In addition to the 13 pin DIN connector for the ACC2 jack, I also ordered a 7 pin DIN for the "remote connector". This jack is usually used to supply a keyline and ALC for amps and things like that. I don't have an amp (yet!) but I have seen a few cases of guys applying some voltage to the ALC line to cause the output to go below 5 watts. I don't do a lot of QRPp but especially during the QRP Foxhunts, I do like to go for broke and really turn things down, so I thought I'd give it a shot.
The idea is that you can apply a negative voltage to the ALC pin to "trick" the radio into thinking it needs to reduce the output to an amplifier. I wired up a 9v battery and a 10k pot for some variability of that voltage and gave it a shot. Unfortunately, I could not get the ALC to change at all, regardless of the voltage. I didn't want to spend a few hours and get nowhere with it so I gave up relatively quickly and I'll have to come back to it another day.
So after all that playing around, I got on the air. There was a RTTY contest on which is sponsored by the British Amateur Radio Teledata Group, or BARTG (http://www.bartg.org.uk/hfrttycontest.asp). This is an "everybody works everybody" contest so I figured I could do OK with my 100w rig. I decided to do a single band entry on 15m since I wasn't going to be operating much and I knew if 15 was open, it'd offer good rates. I spent a fair bit of time CQing and found that my equipment arrangement was probably not quite the best - it seems the air flow behind the 590 is quite lacking and I had the fans kick on at high speed after about 20 min of CQing at 100w. This isn't really unexpected but I'll have to get one of those little fans the next time I'm up at Walmart. I did have a little 2 inch DC fan I hooked up to blow air on the back of the rig and that helped a lot. I thin I ended up with 60 some odd contacts and about 15,500 points. Having never done a RTTY contest before, it was interesting to see who was on. It was nice to be able to surf the web and watch Youtube videos while I operated too, though that did cause me to miss a few QSOs when people responded and I wasn't paying attention! I am beginning to recognize when to turn the beam from NE to NW as propagation shifts, which is something all the experienced ops have figured out to a T.
That pretty much sums up the last few days of ham radio at the W0EA shack. I think for the next blog post I'll try to think of something with some visual elements! This blog needs more pictures!
I've been playing with magnetic loops for a while and I have yet to perfect the science but I'm wanting to do some stuff with my MTR and a small loop on the deck for instance. The problem there is the MTR's receiver is so quiet, I can't tell when I've got the loop tuned like I can on the KX3 with the pre-amp on. Knowing this and that the MTR is a little sensitive to high SWR, I've been avoiding too much playing around since I have to take the KX3 to act as a REALLY fancy SWR meter. Well that all may be over with now.
It isn't a complex design by any means but the unique part is that it gives the transmitter a matched load regardless of the actual impedance of the antenna, protecting those precious final transistors! Since my implementation uses 1/4w resistors rather than the 1 or 2 watt ones you get in the commercial kit, mine is probably limited quite a bit power wise but I didn't feel any heating in the testing I did at 5w, and you don't really need lots of transmitting time to identify if the LED is on or not. Here's what mine looks like:
Since I didn't have a 470 ohm resistor, I just used two 1k resistors in parallel. Not fancy, but it works! To test it out, I put my mag loop at the antenna end and plugged the MTR into the input. Sending a few dahs, it was very obvious I was out of tune. I continued sending dahs into the bridge as I tuned the capacitor on the loop and sure enough I found the dip in luminance on the LED, it was very obvious. I then swapped the antenna to the KX3 to see how close I actually got to the SWR I wanted and I was absolutely shocked to see that it read 1.3:1. The dang thing actually worked! Always a great feeling when something you kluge together on your bench works like its supposed to!
So now I've got a bridge that works but it does need a switch to be truly useful since you don't want to have to plug it in/unplug it every time you want to test SWR. The coax you see in the picture is unterminated too, they're just going into a couple banana-BNC adapters so I'll have to decide how I want that to work too. Anyway, it works so you can be sure you'll see an update on this in the near future as it gets some real world use.
It's been a while since I updated the blog so here's a post on the latest development in the life of my MTR. As you've seen already, its been outfitted with a really slick touch keyer, BNC connector, and an on board 9v battery. Unfortunately it seems my 9v is dying so I decided I'd give this LiPo battery tech a chance. I meandered over to the favorite Chinese location: HobbyKing.com. They have a ton of options for batteries and many other things. I went looking for a 3S battery - they have 3 cells and have a nominal voltage of 11.1v, perfect for 5w output from the MTR. You can get 3S batteries pretty small but I was hoping to max out the capacity while maintaining the ability to stick it to the side of the MTR case, just like my 9v. The ideal capacity ended up being 850mAh, just a bit less than the 1Ah capacity of a lithium 9v, but obviously with a lot more juice at 11.1v. Here's the one I picked:
After picking one of their cheapest chargers and applying shipping, for $21 I had a full setup.
The battery comes with a male JST type connector but I decided to go the more permanent way and just solder the wires directly to the switch I've already got wired up in my MTR.
Here's the battery compared to the 9v its replacing:
The DC-4S is the charger for the LiPo, also very small!
Remember when cutting leads off of a battery like this that you should cut them ONE AT A TIME! Don't ask how I know that.
Anyway, I ground down the one corner of the top case on the MTR (not pictured) and passed the wires into the MTR that way. Unfortunately with these batteries, there's also a balanced lead that you plug into the charger to control the cell balancing. In my case, the charger I got actually charges through the balance wires so it works out OK, I don't have to remove the battery from the MTR in order to charge it!
I am getting 5w on 20m and 4.5w on 40m with the battery at 11.7v, which is about what I would expect since that was roughly what I got with my 8 cell NiMH pack which tops out at about 11.2v. I made a few QSOs on 20m and went outside for a glamour shot. That yellow really looks nice next to the blue!
There's still testing to do as far as how long this is going to last, hopefully I'll get out to the park on Saturday and put it through its paces.
Since I have had my hex beam up, I have not been operating much below 20 meters. The band conditions have been terrible anyway. Still, it has been a goal of mine since then to get up a antenna for the low bands that does not require a tuner. My doublet was working fine, but I no longer needed the multi-band capacity.
This lead me to a number of choices. The most obvious was a basic dipole for 80m, or a fan dipole perhaps. Neither of those options really sounded all that great though. The way I have my antenna farm set up, I don't have room for the full 125 feet I'd need for an 80m dipole, so I'd need something with some loading to fit in my available space. Secondly, I wanted 40m, primarily so I could use my QRP rigs without a tuner, like the MTR. As a bonus, I figured I'd might as well include something for 30m as well.
Wishing to try something new, I decided on a trap dipole for those three bands. AK0M, Steve, works in my building and he has had lots of success building traps for his EFHW antennas he uses at home and for portable ops and he suggested I give it a shot. I had not built any trapped antennas before, usually opting for one-size-fits-all balanced line fed doublets and relying on a tuner to do all the work. He pointed me to an app from VE6YP which can be used to quickly design coaxial traps. His site is here. Simply input the type of coax you're using - there are several built in, if yours isn't there, you can look up the specs you need in data sheets - and it will churn out the turns you'll need for each trap. Based on some research, it is suggested to build your traps for resonant frequencies slightly below your operating frequency. The one article I read had a trap for 40m tuned to 6.5 MHz. I didn't look much into it so I made my traps for 6.5 MHz on 40 and 9.6 MHz on 30. I built my traps out of 1 1/4" 1120 PVC pipe. 1120 has a very thin wall compared to schedule 40 PVC and is perfect for making traps since it is lightweight. I used RG174 coax that AK0M gave me for the coax elements. The schematic for the traps is shown below:
The tuning of the traps is somewhat critical, so you do need test equipment for this project. An older MFJ antenna analyzer is suitable though, and are usually easy to borrow if you don't already own one yourself, which is what I did. You can see a video of how to use the MFJ analyzer to determine the resonant frequency of the traps as you build them.
Its available without a subscription. In the article, K4VX builds a 40m dipole using 450 ohm ladder line to linearly load the antenna, resulting in a 30% reduction in total length. I scaled the lengths for 30m and built mine up, allowing for a fair amount of length for tuning purposes. I didn't keep track of my lengths but you can calculate them easy enough.
I proceeded to hoist the antenna up to the top of my mast to tune the 30m section. Remember to tune WITH the traps in place, since they do add a bit of loading. A few trips up and down and the 30m element was tuned in just fine. After reading K4VX's article, I basically left the loading section (the 450 line) alone and limited my trimming to the 30m wire, this is important and you'll see why soon.
Being unsure where to start with the 40m wire, I measured from the center, 33' as if I were making a full size 40m dipole. Of course it resonated far too low, at nearly 4 MHz! I started lopping off several feet at a time until I zeroed in on 7 MHz. As I got close, I checked the 30m resonance and found that it moved down in frequency a bit and was no longer in band. This is where I started trimming the loading section. I took 3 inches off at a time and pulled the 30m part into range again while trimming the 40m section too. This took a really long time. I was being extremely cautious to avoid over-trimming since it was looking like the usable bandwidth on 40m was going to be close to only 70 kHz. A bit too short, and my goal of a no-tune antenna for 40m CW would be lost. Finally both 30m and 40m were in tune and I added the wire I had left over to the ends for 80m. Again, both 30 and 40m sections were slightly affected by the additional wire so I trimmed another 3" off the loading section, and a bit more off the 40m section. A couple more trips up and down the mast awarded me with 3 bands in perfect harmony, providing <2:1 SWRs in the spots where I wanted them. HOORAY!
A piece of one side of the antenna, the center is at the mast under the hex beam. You can see coils for 40 and 30m here.
It was about this time that I realized how short this antenna was. The doublet it was replacing was about 88' long when I took it down (it was 100' when I put it up, before I trimmed for that "magic" length). In comparison, this thing was dinky. I suspect I could have done without the loading all together, but we live and we learn! I just hope the efficiency does not suffer too badly. Time will tell. The good thing about antennas is that nothing is permanent, we can always put something else in its place!
I have not had sufficient time to put it through its paces, and with the band conditions as poor as they have been lately, now would be the worst time for a real assessment of its performance. Keep an eye on my twitter (@w0ea) for up to date reports from the shack.
I got the new Micro-Matcher (as I've begun calling it...) out to the park today for some more intensive testing with an antenna up in the air with no distractions. I went to my usual spot in Bever Park and put up the PAR wire (~40') which again, is designed to work on 40, 20, and 10m. With the PAR matchbox, I had flat SWR on all bands and across the whole band. With the Micro, it was not quite the case. Luckily, in the CW portions of the bands, SWR was spot on. However, in the voice portion, that was not the case. It seems the small (dinky!) toroid was making the match much higher Q, and thus much lower bandwidth. This is no surprise, but it isn't all that bad. With the PAR wire being in tune in the CW portions of 40 and 20, it will still serve its purpose as a super tiny matcher for use with my MTR. When my new wire gets here, I'm going to replace the heavier wire used on the PAR with the lightweight 26 gauge poly-stealth, and it should work just fine.
I also tried a 66 foot wire with both matchers. The 66 foot wire is a half wave on 40m which means its a full wave on 20, 1.5 halves on 15m, and 2 full waves on 10m, all high impedance feedpoints when fed at the end, so it should work with both matchers. Unsurprisingly, the PAR matched on all 4 bands without any trouble. Very cool to pick up 15! Unfortunately, the Micro simply did not have the guts to get decent matches (<2:1) on any band. I may have been able to trim to get a better match but I trimmed it to a perfect match with the PAR and I didn't want to lose that.
So, we've learned some lessons: the FT37-43 cores are too small for a wideband transformer like the PAR. They DO work for a limited bandwidth match though. If you have the parts in your junk box, build away I say! I wouldn't go mass producing these by any means but I did make contacts on 20 and 40 with mine so it isn't snake oil. I might make one with a bigger core just to see if it matches as well as the PAR (no reason it wouldn't).
Have fun experimenting, but don't come crying to me when it doesn't work! :P Good luck at Field Day this weekend, hope to hear you all on the air. 73!
EI've had a PAR End Fedz antenna since I had my K2 (it came with one direct from Dale Parfit himself) and used it extensively for portable use for a long time. Since then, I built (and blogged about) a AA5TB style EFHW matcher that uses a fixed coil and a variable capacitor on the high impedance side of the circuit. That post is here: http://w0ea.blogspot.com/2012/08/aa5tb-end-fed-half-wave-tuner.html
With my MTR project wrapping up, I thought I could retool the Par antenna to make a really tiny and lightweight EFHW even more minimal than the one I built before. The idea was to replicate the PAR matcher since it does not require a big, variable capacitor. Luckily someone had already torn into that black box and found what was inside. (that article is here) I stole his nice graphic depicting the circuit, it'll also take you to the article.
It is very simple: a 150pF shunt capacitor and a 9:1 transformer (3 primary turns, wound bifiliar, 27 secondary turns). The article mentions that the commercial unit uses an FT87-43. I built mine with an FT37-43 because that is the smallest I had on hand. The raw circuit built up is below:
Yeah its that small!
Once I proved the concept worked, I did some brain storming and figured out the perfect housing for this little devil: the screw on part of a PL-259 connector.
I added an eyelet imbedded in the glue in case I need to tie off the end
A couple of washers close up the feed point end and a #4 screw is held in place to connect the radiator
