So I get my new tuner tomorrow. A few questions...

[W5BRM]

I bought a MFJ 969 manual tuner. I also have a 50ft length of 450 ohm ladder line and a MFJ 4602 window pass through. My intent is to string up a 40m inverted V fed with the ladder line.

Does the ladder line need to be a certain length to work with the tuner if I want to work 30-10m? As the antenna will already be tuned for 40, I shouldn't need it on 40 or 15m. *sidenote* I will have to trim a couple foot section off to use the window pass through and connect to the tuner inside the house.

What kind of losses can I expect if I use *random* length of ladder line and on what bands?

Will I need any sort of Balun to get it to work? I believe the 969 has a 4:1 built in balun but I don't know if that will be enough or if it can be bypassed.

If I do happen to screw up cutting the dipole for 40m, will the tuner be able to take care of any mismatch? (Remembering my other disasters in making dipoles, I DO have new coax as well but thinking ladder line will be easier to work with... I hope anyway)

[KG4NEL]

As long as you're not asking too much of the antenna system, I think you'll be fine. It's likely a voltage balun, and probably not rated for much - but it should work on 80-10 with that much wire in the air. I'd be wary of Top Band.

The short answer is no, the ladder line's length is irrelevant for the most part. Yes, you can adjust the length of the feed in order to bring the system to resonance (W5DXP's multiband setup does this with manually-thrown switches to take lengths of line in and out) but if you have a tuna already then it's superfluous.

Beefy 1:1 current baluns are not cheap, but start running any kind of power through a mismatched antenna and the voltage has to go somewhere :)

[WØTKX]

http://www.hamuniverse.com/tuner.html


Now Let's learn how to "tune" that "tuner"

Most antenna tuners have an inductance rotary switch and two capacitors. (refer to photo at top of page) The capacitors are often labeled ANTENNA and TRANSMITTER. In some antenna tuners the inductance switch is replaced with a continuously variable inductance, popularly known as a roller inductor.

Let's assume you're using a tuner with an inductance switch, because they are the most common.

SHOCK HAZARD! NEVER TRANSMIT WITH THE TUNER COVER OFF AS IN THE NEXT STEP!
TURN OFF THE POWER TO THE RADIO!

Place both capacitor controls at their mid-range positions. Don't trust the knob markers if this is your first experience with the tuner! If you are comfortable with the next procedure, remove the cover of the tuner and turn the knobs until the moving capacitor plates are only half meshed with the stationary plates. If the knobs are pointing to half scale with the reference markings on the knobs and front cover, consider yourself lucky.

If not, loosen their Allen screws and rotate the knobs so that they point to mid scale.
Re-tighten the knobs, replace the tuner cover and you're ready to go.

Turn the radio on and tune receiver to an un-used frequency on the band you desire, listen for a few seconds, with the antenna and transmitter controls at mid scale, move the inductance switch to each of it's positions until you hear the loudest noise or signals coming into your radio.

Then, rotate the antenna and transmitter controls until you get to the absolutely loudest noise or signal level on the radio. All three of these controls interact with each other so practice on several bands to get the "feel" of the procedure.

Select your final band of operation and repeat the procedure above. When noise peaks out using your ears and the S meter, your tuner settings should be very close for final operation.

With your rig set to low power monitor the frequency to assure that it is not in use, send your ID then transmit a continuous carrier while you tweak the antenna and transmitter controls for the lowest reflected power reading with the highest output power as read on the Swr/Watt meter.

You may find that you have to vary the position of the inductance switch a position or two either way to get your best match.

Play it safe and un-key before turning the inductor switch...un-key first....turn the switch...key up....repeat as needed until lowest SWR and maximum output. Be gentle to your radio; keep the key-down periods as short as possible. Depending on the impedance at the antenna input (and the overall design of the tuner) you may not be able to obtain a flat 1:1 SWR on all frequencies and bands.

Also important to remember is that your Swr will change, go up, as you tune further away from the frequency you used to "trick" your radio! So re-check and re-tune as needed as you move around the band.

You can get an idea of your SWR bandwidth by starting with your original frequency, and using the procedures above withlow power, (don't move any knobs or switches after best setting)....sweep or tune your VFO up and down the band while watching the SWR readings and note the frequency where the SWR reaches 2:1 at the higest and lowest frequency. Stop there!

Example: If your on 40 meters at say...7.262mhz as your starting point, and your SWR is 2:1 at 7.292mhz and the highest swr going the other way is 2:1 at 7.259mhz, then your "safe tuning range" without retuning the antenna tuner would be about 60khz.

Keep in mind to use very low power and ID because your signal may be heard for a split second as you tune across the band! When that transmit key is down, someone somewhere can hear you. Even a dummy load gets out somewhere!

Remember your "TRICKING" your way around a good antenna!

[NQ6U]

Whenever I put up a new antenna or modify an old one, I connect my antenna analyzer to the "transmitter" side of the tuner, set it for the frequency of interest, adjust my tuner for minimum SWR indication then record the settings for use with my transmitter. Not only does it save a bit of wear and tear on the transmitter, it cuts down on QRM on the band.

[WØTKX]

Yea, but I don't think he has an analyzer. yet. ;) But this should be inneresting.

I'll never forget my amazement years ago when I switched to balanced line for RF.

[W5BRM]

I've got a MFJ 259c. That was another question rattling around in my head like a pebble in a tin can. Hooking up the analyzer and tuning the antenna that way. Does the 969 have to have a minimum wattage applied for the tuner to work? As i think it's a mechanical tuner and not electronic/auto, i don't think it does but I'm not 100% certain on that

[K7SGJ]

I've got a MFJ 259c. That was another question rattling around in my head like a pebble in a tin can. Hooking up the analyzer and tuning the antenna that way. Does the 969 have to have a minimum wattage applied for the tuner to work? As i think it's a mechanical tuner and not electronic/auto, i don't think it does but I'm not 100% certain on that
No minimum to function, but the higher you raise the output, the more reflected power you will see on the meter making it easier to "fine tune" the tuner for minimum reflected. Tune at low power and gradually raise it to your operating power tweaking it as you raise the power.

[KG4NEL]

I'll never forget my amazement years ago when I switched to balanced line for RF.

Notably, thinking..."that shit radiates?"

:mrgreen:

[WØTKX]

Actually, how little the feedline radiates when hooked up to a doublet.
And properly matched with a so called "tuner". The power wants OUT!

;)

[W5BRM]

Tuner is here but it too freakin cold outside to mess with it...lol. I gotta trim the 1x4 and 1x2 that MFJ included for the window passthrough. I'll do that later.

Thanks for all the info