Archive for the ‘antenna’ Category
We're done with the editing of Episode #164 and here it is for your listening pleasure. In this episode, your hosts tackle topics from Bugbook computers to permanent amateur radio licenses, from Turing phones to Raspberry Pi computers and from antenna modeling software to lobster on pizza. We hope everyone will find something to enjoy. Please let us know by sending us feedback. We'd love to hear from you.
73 de The LHS Crew
The BLT-Plus Balanced line QRP tunerI was looking for a QRP tuner for the 1Watter 40m transceiver I am building that would work with both balanced feedline antennas as well as coax feedline. The traditional Z-Match tuner is quite efficient at tuning balanced line antennas and the built-in SWR bridge gives you an all-in-one tuner and SWR indicator without having to take a separate SWR meter along with its inherent mess of cabling a separate SWR meter. The BLT in the name stands for "Balanced Line Tuner".
|The Kit as it comes out of the bag|
Why use a z-match ?
- Matches balanced loads without the use of lossy baluns.
- Being a parallel resonant circuit, the Z-match can provide some band-pass filtering for your receiver and harmonic attenuation for your transmitter.
- A well-designed Z-match tuner has a high Q and is more efficient (less lossy) than other types of tuners.
- The fixed inductor simplifies construction (no taps or rollers needed).
The secret sauce
Built in SWR indicator
|SWR bridge with LED indicator|
|Switch to Tune to present a low SWR to the transmitter while matching, switch to Operate when finished|
- The kit is provided with really nice water slide decals that give it a commercial look (if you don't ruin them like I did). The instructions recommend applying a clear coat to the decals after they are applied. I used a Krylon matte finish clear coat which indicated it was fine for metals and plastics but it partially melted the decals and caused them to bubble. I'd suggest testing whatever you are going to clear coat them with first.
- Don't over tighten the plastic tuner shafts or you won't be able to slide the knobs on (yes I did).
- The binding posts have little plastic spacers that separate and it isn't obvious. If you install them and wonder how they don't ground themselves (like I did) you've done it wrong and will have to go back after it's together and try to remove them with all the wiring in place.
- The bolts for the binding posts are very soft metal and the nuts can strip them if you apply too much force (yep I did that too).
- The main toroid has three sets of windings and they overlap. Pay attention to the instructions about winding them all in the same manner (clockwise or counter clockwise) or you will have to rewind them (yep, I did that too).
- The 3 windings on the main toroid overlap so you won't be able to go back and verify your turns when doing the 2nd and 3rd winding so count carefully (ask me how I know).
- Temporarily attach the SWR bridge to the front panel to get the spacing correct to solder the LED leads.
|My messy toroid winding... but it's working fine|
- Connect your transmitter and antenna.
- Choose the appropriate switch in the back for coax or balanced line antenna (Up for coax, Down for balanced line).
- Start with the inductance switch on the back set to low-impedance (Low-Z) because it is the most efficient. It uses the 6 turn secondary rather than the 12.
- Switch the front switch to "Tune"
- Key the transmitter and be sure you are using 5 watts or less
- Turn the "Load" knob first until you see a dimming of the LED then the "Tune" knob to make it go out completely
- The knobs interact so you'll need to go back and forth between them to achieve best match
- If you can't get a good match switch the inductance switch on the back to "High Z" and try again
- Don't apply power too long at a time during tune because the 50 Ohm resistors are heating up in there during the Tune process
- When the LED goes out or gets very dim you have a very good match. Switch to "Operate" and enjoy a well matched antenna
|Result of having to rewind the secondaries made it messier than I'd like|
Five by Nine... QRP... How can it be?
I gave him reports as he switched back and forth from running barefoot ~75w to his amp ~500w. With his amp on he was an S9, running barefoot he was S8. So the amp gave him one additional S unit. In terms of hearing him I would have been hard pressed to tell much difference simply by volume. He was perfectly copyable without noise with the amp off.
We also did some tests with my station at reduced power (as if...) At 10w-12w output I received a S9 to S9+10. Reducing output to 5 watts netted me a S8 report and when I reduced to 1 watt (one watt) he was still able to comfortably copy me and I received an S5. So with my station at 1 watt and his running 500 watts we could still converse via SSB. Ladies and Gentlemen you don't need as much output wattage as you think you do.
He was running through a newly constructed homebrewed vertical while I was using my 80m OCF Dipole. We didn't discuss what sort of radial system he had installed, but the difference in antennas was likely the deciding difference in our stations. We were about 500 miles apart and his vertical probably had more low-takeoff gain than my dipole, or possibly more ground loss so I probably had better high angle gain on him for the short 500 mile skip. I think the take-away from this exercise is that the antenna is generally the key rather than transmitter power. If I can get 6 dB of gain from my antenna I have in essence quadrupled my effective radiated power. Quadrupled? Yes, Quadrupled effective output power.
Power and S-Units
- A Power Ratio: dB = 10 Log P2/P1
- A Voltage Ratio: dB = 20 Log V2/V1
You increase 3dB each time you DOUBLE your power
You increase 3dB each time you DOUBLE your power. So to gain one S-Unit you must quadruple your power.
Antennas offer the cheapest increase in dBNote the statement above "using the same antenna system". That's the key then isn't it? It's easier to get 6 dB of gain from an antenna than from wattage. A 40m doublet can offer significant directional gain especially when operated on higher bands. Now unless it's rotatable you will be at the mercy of the directionality of its lobes but if you have trees or tall structures you can very cheaply string up a few dipoles oriented in different directions and for far less money that a 500 watt amp (6 dB). If you can only have one wire antenna you may miss out on some DX in the antenna's nulls but you will have some stellar gain in the direction of the lobes. Of course rotatable yagis and beams are the best but now we are talking about real money again. I'm talking bang for the penny. You don't have to buy a wire antenna. Some Dacron rope or weed-eater line and some surplus insulated wire is all you need. You can even make your own feedline cheaply from electric fence wire and insulators.
We have a great hobby, but there are so many aspects of it that sound like common sense when they really are not... like increase your power.
Increasing power gains you very little compared to a better antenna systems. Put that in your 811A amplifier tube and smoke it !
That's all for now.
So lower your power and raise your expectations (or your antennas)
72/73 (Note: 72 is a common substitute for 73 among QRPers... as in "not enough power for 73")
Elecraft CP1 - A tasty RF treat
|Elecraft CP1 Kit|
Couple what?Ah, so if your new to this like me you might be asking what does a coupler do? Well it sorta listens in on the signal going out (forward) and reflected (back) and is able to send an attenuated sample of the signal to other devices. It attenuates the sample by either 20db or 30db depending on how you build the kit.
The 20db version is good for signals 25 watts and less so that's the way I built it. It was easy to build but my glue under the second toroid wasn't strong enough and you can see it popped up a bit. Also the Elecraft instructions had one confusing instruction concerning mounting the toroids. The instructions say "... When wound and mounted correctly, the enamel wire will emerge from the top of each core and connect to the top hole at each inductor location". Well when you wind a toroid only one of the wires can "emerge from the top of the core" while the other comes from underneath. This confused me for a minute until I finally just went on with the install. Anyway, if you're a stickler for following instructions that one may cause a moment of pause...
The switches for the two outputs forward, reflected (J3, J4) are in the up position when they are not in use. When the switch(es) are in the up position the 50 ohm 3 watt resistor(s) take the place of the switched off output. Don't disconnect an output and leave the switch in the bottom position. I'm not sure what will happen... maybe nothing, probably a bit of a mismatch on the SWR, or maybe it could be like "Crossing the streams" in Ghostbusters. Your mileage may vary.
My uses for a couplerMy old Ten-Tec Century 21 has an analog VFO dial that gives me a good guess at where I'm at but I use an external frequency counter to give me more information. I had it sorta rigged my frequency counter to sample the signal from RF leaked on the shield but I didn't really know how much power I was sending to the counter so this coupler allows it, as well as other devices, to be safely connected to the transmitted signal.
I also plan to use the coupler for IMD tests using a oscilloscope and other projects. It's handy device to have in your collection.
But in the end - It works
It looks like my tri-band Par antenna, which should be a good match on 10m, 20m and 40m is faulty. It is a good match on 10m, but only on 20m and 40m via the ATU. Tomorrow I shall try loading it up as a long wire tuned against ground via the ATU. Somewhere I have a Sandpiper Poliakov vertical that I should erect. As I recall this has a 9:1 unun so it matches well on most HF bands via an ATU.
Even soldering on a coax is hard work these days! Oh to be fit.
At the moment I am on 630m WSPR using the earth-electrode “antenna”.
Calling QRP CQ - Inconceivable
Amazingly my 80m Windom / OCF Dipole has 4.5:1 SWR native around 1.8 mHz and it matches easily with a tuner across the entire 160m band. That was a surprise.
I tossed my mighty 5 watts call out at 1810 kHz not expecting much...
So how do you know if and where your signal is getting out ?
The Reverse Beacon Network
|Map of the last 100 reports from Reverse Beacon stations of my call sign|
Color coded by band
It even includes a speedometer
|My brief speed key session with N4HAY|
My shack is fairly spartan. Just the IC7000 as a main rig. The antenna farm is equally so with all antennas in the loft bar a 2m & 70cm colinear.
Its a fairly spacious loft mind you. Enough room for a Watson 80 plus 2 dipole (Which they don’t seem to make any more) with extra elements for 30m and a 4 element 10m band yagi. But 80m is really not working for me.
So with a few hours to spare this weekend and a bit if ladder line I pulled together a W3EDP antenna. Its nothing new and a very cost effective antenna. So without going through all the detail it was either that or nothing at all for 80m. I just simply don’t have the space for a windom ( which is what I would have preferred) and G7FEK limited space antenna would have meant more stuff in the garden to annoy the XYL.
Needless to say I got the chance to try it out, firstly with the Hack Green SDR and shortly afterwards a nice QSO with Peter, G4LHI in Huntingdon.
So for a couple of hours work I can recommend the W3EDP. Noting of course the current at the end and need for a good counterpoise / earth. I can also say that even in a lash up configuration it withstood some pretty big winds here in IO84 this weekend.
So where to find out more:
Well a simple Google will give you most of the info you need but you could do worse than invest in the the Stealth Antennas book. I have a copy of the older version,
I see the new one has a different cover, I’m not sure if there was much change in the insides between editions but there’s something in there for everyone. From ultra small weird looking things to some old favourites like loops and verticals all the way to ultra cheapo types.
Its not all good news though. The XYL isn’t happy with the wire. The Watson 80 plus 2 (whose inspiration came from the G4ILO section of this book) didn’t quite meet my expectations and I didn’t quite get the G7FEK constructed. Maybe next time.
If you’re stealthier on 80m then I’m sure I won’t be the only one who is interested in finding out how you did it. If not then lucky you for having enough garden and don’t forget to listen out for the weak signals.