Newbee Topic #2- Tuning Up Tuners

[ky5u]

You got that new shiney HF rig and an external tuner. Now what? Here are a few somple do's and don'ts.... This is in no way a full course on tuners.

Always tune up with the lowest possible power until your tuner reads minimal SWR. I recently came across an older amateur who had never used a tuner and burned up his radio and dipole center insulator trying to tune his tuner. He was tuning at 100W with prolonged keydown in the CW mode.

If your rig has an internal tuner but won't tune your antenna, MFJ makes a tuner extender box that might help. This simply adds electrical components that either shorten or lengthen your antenna electronically so it falls within the range of your tuner.

Nothing beats an antenna cut for the frequency you intend to operate on. In this case you don't need a tuner. Conversely, if you buy a 100' spool of #22 wire and hook one end to the "random wire" bannanna jack on your external tuner, then ground the tuner VIA a ground rod, the tuner will function on all bands pretty well. My rule of thumb is that if the random wire is shorter than 76 feet, your results will vary wildly. In my case the 100' of #22 wire is stapled to my wooden fence in the backyard.

Also remember that commercial antennas are rated for a power in PEP. A 200W antenna may destruct at 100W dead key for as few as 30 seconds. Commercial antennas that use coils and traps can be toasted by long keydowns at rated power. The rule of thumb is for constant carrier or high occupancy rate modes, use 1/3 (one third) of the antenna's rate power as your ceiling. So a 1500W dipole can take 500W AM Carriers as a practical maximum.

So here's the poop...

Tuning an external tuner should take no more than 15 seconds. If your tuner has a A,B,C,D, etc. inductor switch, set this switch to deliver the most signal with your rig in receive. Start with transmitter/tune and load apacitors mid range. Apply 5W or less to the tuner (on your intended operating frequency) and set the tunable controls for minimum SWR. If you can't get it flat, try moving the inductor switch setting up or down one position and tune again. Never move the inductor switch with the rig keyed.

If you're using an external tuner and your rig has an internal tuner too, there is no harm after tuning the external tuner to hit the tune button on your rig also. Or simply turn the internal tuner off.

If you're using a tube rig with an external tuner, tune the rig to give you about 5-10W out (100W rig) and ensure the plate current is not too high. Tune the external tuner quickly, then tune up your rig per the manufacturer's instructions. Touch up the external tuner if necessary.

If you're using a tuner on your high power linear amplifier, make sure the tuner is rated to handle the power. Tune the external tuner with the amp in standby. Try never to tune a high power tuner with full power applied unless the tuner is rated for "continuous carrier" at the power being used. Ignoring this enhances the "arc and spark" potential.

I am sure others can add their "true-isms" to this...

[kl7aj]

I'd like to add a bit more about using receiver noise for tuning. With a modern receiver, if you carefully tune for maximum RX noise, you won't even NEED to transmit. Modern receiver front ends are VERY close to 50 ohms, and by reciprocity theorem, if your receiver is matched, so will be your transmitter. This wasn't the case in the old days, where receivers had antenna trimmers and preselectors with impedances that could be FAR from 50 ohms. On my Ten Tec Jupiter, at least, if i carefully tune for maximum noise, the transmit SWR is ALWAYS less than 1.5:1...certainly as good as it ever needs to be.
(I have the built in autotuner, which I hardly ever use, except for going mobile.)

eric

[wa9cwx]

Not bad.

Two points, an effective radial system (counterpoise) is needed for a random wire antenna to work efficiently.
A DC ground, (ground rod) may or MAY NOT offer a useable RF ground. On the lower frequencies, a ground rod in poor soil is basicly useless, and will result in lost RF running around the shack, looking for something to get into. http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

Point two, just a suggestion, when pre-tuning your tuner listening to the background noise level on your receiver, TURN OFF the AGC, or at least, use the FAST AGC position. Makes a big difference in quick tuning accuracy.

OK, a third point, make all grounds directly TO each piece of gear, from one common point, not chained one after the other.....

Me done.

[KB1KIX]

These are great topics.

These should be added to the hamwiki.

http://www.hamwiki.info

Jonathan

[K4GUN]

Again, an awesome primer for us new guys. I do want to ask a question about this. If I am listening to a frequency and I decide I want to transmit, should I tune the tuner directly on that frequency or should I move off a bit so as to not interfere with other users?

I have been tuning by lowering my power to about 15% of max and switching to RTTY and keying the mic. I have an SCG Mac200 tuner and it doesn't always want to tune quickly. I really don't know if being on the same frequency but in RTTY will mess up phone conversations on the same frequency.

By the way, the comment about the AGC was quite useful. I'll switch that off the next time I'm on. I didn't realize that would make tuning more difficult.

[ky5u]

Quote[/b] (wa9cwx @ May 01 2007,09:48)]Not bad.

Two points, an effective radial system (counterpoise) is needed for a random wire antenna to work efficiently.
A DC ground, (ground rod) may or MAY NOT offer a useable RF ground.
Very valid points. But here is a caveat. If you have several dipole antennas like I do, the ground/shield of the coax carries your counterpoise from each dipole antenna into the shack and in my case to an antenna switch. So I run a regular coax jumper from one of the unused external tuner ports over to the antenna switch which effectively adds all the various dipole counterpoise systems to that external tuner for the random wire to use. http://www.qrz.com/iB_html/non-cgi/emoticons/cool.gif

[kl7aj]

Quote[/b] (k4gun @ May 01 2007,10:22)]Again, an awesome primer for us new guys. #I do want to ask a question about this. #If I am listening to a frequency and I decide I want to transmit, should I tune the tuner directly on that frequency or should I move off a bit so as to not interfere with other users? #

I have been tuning by lowering my power to about 15% of max and switching to RTTY and keying the mic. #I have an SCG Mac200 tuner and it doesn't always want to tune quickly. #I really don't know if being on the same frequency but in RTTY will mess up phone conversations on the same frequency.

By the way, the comment about the AGC was quite useful. #I'll switch that off the next time I'm on. #I didn't realize that would make tuning more difficult.
Unless your antenna has a Q of several hundred, it's safe to tune off a few KHZ. On H.F., if you're within 50khz, you shouldn't normally need to retune! An exception would be a very short whip on 80 meters.

eric

[kr2d]

Another tip, something I learned the hard way.

Say you have a random wire antenna as discussed above. You can fold the end of the wire over and stuff it into the center of the SO-239 on your tuner. That isn't a very secure connection, and I don't recommend it because the wire can fall out. That happened to me on more than one occasion. A sure indication of that happening is that you cannot tune your antenna no matter how hard you try.

If you suspect that your wire has fallen off of the connector on the tuner, DO NOT REACH BACK THERE AND CHECK WHILE THE KEY IS DOWN! RF burns hurt like nothing else, and take months to heal.

[kb2vxa]

Hi 4GUN and all,

"If I am listening to a frequency and I decide I want to transmit, should I tune the tuner directly on that frequency or should I move off a bit so as to not interfere with other users?"

ALWAYS tune on top of them, the complaints you hear are a good indication of how well they're receiving you. http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif

[KE4YGS]

Great info even for experienced Radio folks. The comments seem to be directed toward random wire antennas, however will the same procedures work with a trapped say 6 band vertical? I have a 100W rig with AT but the internal tuner won't tune the swr out except on maybe 10 Meters. It took months to get everything together to just get it mounted ( set exactly to Mfr. Specs.) and sooner or later I'll get a cherry picker to get up there and adjust the traps but in the mean time I'm thinking of an external tuner. Any suggestions?

[wd0ct]

T network tuners with 3 continously variable controls can be a pain. Preset either the input or putput C to max capacitance and see if it will tune as described above. It more than likely will.

Efficiency will be improved and tuning will involve only 2 controls from then on.

Log your settings.

[ky5u]

Quote[/b] (KE4YGS @ May 01 2007,13:55)]Great info even for experienced Radio folks. The comments seem to be directed toward random wire antennas, however will the same procedures work with a trapped say 6 band vertical? I have a 100W rig with AT but the internal tuner won't tune the swr out except on maybe 10 Meters. It took months to get everything together to just get it mounted ( set exactly to Mfr. Specs.) and sooner or later I'll get a cherry picker to get up there and adjust the traps but in the mean time I'm thinking of an external tuner. Any suggestions?
Yes the tips work for all antennas using an external tuner. The random wire example was used because that's one of the more difficult antennas to get to load on multiple bands without a tuner and one of the antennas most useful to those who live in restricted neighborhoods. It is also most like what you find with verticals where the ground side of the vertical needs ground rods or radials.

With your vertical traps out of tune what you really have is a vertical wire/tubing of unknown electrical length same as a vertical random wire, right? A tuner should help you alot provided you have a decent ground system.

As for what to get, I just bought an MFJ "Versa Tuner II" used off of eBay for $35 bucks. I use it on a set of Kenwood Twins to tune a dipole at over 100W. Most any of the MFJ 200-300W tuners would be good. Get one with a built in wattmeter/swr meter and be sure to ask the seller if the meter works properly.

[KI4SQT]

I bought a used palstar tuner from a real gentleman of a ham K9ZK, it is a Palstar 1500 and my first with a roller inductor.
His suggestion to me was to put the radio/tuner into a good switch, hook in a decent antenna analyzer (MFJ 259 B) not bad for the money, select your frequency on the analyzer, tune your tuner to flat SWR and in my case tune my tube type transmitter (TS 830 S) into a dummy load. This creates a great match with no load on your transmitter, and no interference to the bands.
Just a thought.
Thanks

[N4AUD]

If you've got one, use an antenna analyzer to tune. It transmits a very small signal.
Once you are tuned, write down the settings for that band and frequency on a 3x5 card. Keep that card handy, and when you change bands and frequencies, it will help you get you in the ballpark.

[N4AUD]

Oh, if you have a built in tuner but you are using an external tuner, don't forget to turn the internal unit off.

[K8YZK]

A couple of things I want to add, and I know one was said before.

Log the settings that are on the tuner. That way you can quickly go back to the settings when you switch bands. I always have 3 settings for each band top/bottom/middle.

Also it's nice to have a 1:1 swr, but anything around 1:1.5 is good, because I know not all antennas or tuners will find that supposely magically 1:1.

Kurt

[kl7aj]

Quote[/b] (wd0ct @ May 01 2007,13:59)]T network tuners with 3 continously variable controls can be a pain. Preset either the input or putput C to max capacitance and see if it will tune as described above. It more than likely will.

Efficiency will be improved and tuning will involve only 2 controls from then on.

Log your settings.
For three continuously variable components, here's a simplifying trick. If the antenna is known to be a high impedance, adjust the OUTPUT capacitor for max and tune the input cap and inductor for a match. If the antenna is known to be a low impedance (short), set the INPUT capacitor for max and adjust the inductor and output cap for a match. In this manner, you're treating the tuner like a simple L network...avoiding the multiple match syndrome. Also, this will acheive the greatest efficiency under nearly all conditions. Read W4RNL's page on this matter. He's done his homework!

eric

[ky5u]

Quote[/b] (kl7aj @ May 02 2007,09:45)]If the antenna is known to be a high impedance...
The newbee won't know this in all probability. Hence my advice to start with the caps in the midrange position.

[kl7aj]

Quote[/b] (AG4YO @ May 02 2007,09:51)]Quote[/b] (kl7aj @ May 02 2007,09:45)]If the antenna is known to be a high impedance...
The newbee won't know this in all probability. Hence my advice to start with the caps in the midrange position.
But he should be able to determine that, after getting a good match a few times.

Which brings up an interesting point. With just TWO continuously variable components, you can match any load to any source, if you can switch polarities (low to hi-Z or high-to low-Z, so one might think that having three infinitely variable components is redundant....you theoretically could have an infinite number of combinations for a perfect match.

However, one thing you can do with three continuous components is adjust matching and PHASE shift independently. Using two such antenna tuners in a phased array allows incredible versatility for matching and steering. You do need a good phase monitor though!

eric

[W4HAY]

I use a homebrew Wheatstone resistance bridge (from ARRL's Antenna Book) with a slight modification: I dump the transmitter's output into a dummy load (you DO have one, don't you? http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif ) and sample the power through four 100 Ohm, 2 Watt resistors in series to the input of the bridge. Thus the transmitter sees essentially a constant near-50 Ohm load and the antenna only gets a fraction of a watt during tuneup. A DPDT switch removes the dummy load and bridge from the circuit and connects the antenna to the transmitter output for normal operation.

While only a small amount of power gets through to the antenna, you can still be heard! I was plotting a tuning chart on an 80 Meter dipole late one winter evening and had a station several hundred miles away call me. We enjoyed a lengthy milliwatter QSO.