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Bird RF Watt Meter Questions

Sniper308 said:
Im searching everywhere online for antenna tuners but I cant find one for power over 300w.
Click to expand...

I was looking at MFJ tuners and found this one.
MFJ Enterprises Inc.
I'm new to antenna tuners so I'm doing research on what's good out there. I checked reviews on EHam about the MFJ-945e. That's one I would definantly stay away from. Too cheaply built
The 948 touts as being arch free
 
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Lil'Yeshua said:
I was looking at MFJ tuners and found this one.
MFJ Enterprises Inc.
I'm new to antenna tuners so I'm doing research on what's good out there. I checked reviews on EHam about the MFJ-945e. That's one I would definantly stay away from. Too cheaply built
Click to expand...
Personally I would stay away from MFJ tuners. I've had a few and they all are junk.
 
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Contrary to popular belief, all MFJ tuners are not junk. That '989 is a good one and so are several others with the abilities you want (that 300 watt rating). I would suggest finding one that has at least half again as much power rating as you ever contemplate putting through it. That's any brand, not just MFJ tuners. The greater the impedance mismatch the greater the power rating should be.
- 'Doc
 
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I agree.

I have had many MFJ tuners. The only ones with problems were bought second hand from abusive users.

I've also owned several other MFJ products and enjoyed them all. I admit, some products have some fit and finish issues, but not a deal breaker. I like their adventure radio series, pretty cool stuff.

I've seen many a HAM struggle with trying to use a tuner correctly, especially when they want to load a 10 meter dipole for 80 meters.

It's usually an MFJ tuner that gets a bad rap since it's usually the cheapest tuner option on the market. Most EHAM commandos bad mouth stuff because they can't figure out how to use it.
 
When the amp is on, it provides the SWR load that the radio sees. The antenna is now only responsible for the SWR the amp sees. If you want to try and use a tuner to assist with the problem of protecting the radio, consider it only has to handle the power of your radio, not the amplifier since it will be between the radio and amp
 
Shockwave said:
When the amp is on, it provides the SWR load that the radio sees. The antenna is now only responsible for the SWR the amp sees. If you want to try and use a tuner to assist with the problem of protecting the radio, consider it only has to handle the power of your radio, not the amplifier since it will be between the radio and amp
Click to expand...

Good point. I didnt think of that. I guess this is overkill then?


Palstar.com: HF-AUTO 1500 Watt Automatic Antenna Tuner
 
If your goal is just to give the radio a good SWR with this amp, it should cost a lot less to fix the problem in the amp than it will to buy that 1500 watt antenna tuner. Keep in mind that using a low power tuner between the radio and amp will not completely restore the power lost in the mismatch between the radio and the mistuned amplifier. This is not likely to be a significant factor but this approach is a cover-up. Although, it will protect the radio from seeing the poor reflected power.
 
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A tuner is only an impedance transformer. Just like one you plug into the wall to get 9vdc from 120vac, it only changes/matches impedance instead of voltage. That changing, or matching is done -quite- often with a lot of antennas only it's done at the antenna instead of sitting on a table by the transmitter (gamma, beta, 'trombone', delta matches, etc.). It's a simple fact that the input impedance of almost all antennas is very, very seldom 50 ohms with out 'help'. Those coax length thingys do exactly the same thing, just in a different way.
"But tuners have losses!", yep, they sure do. But those losses are typically very small in relation to the loss you'd have if it wasn't used. (Back to those gamma, delta, etc, impedance matching devices, same thing.) Any, and everything, you insert in a feed line contributes losses of some size or other! If those losses amount to less than not using one, then you are better off. That's the whole point of matching impedance to begin!
Can a tuner be used incorrectly? Good grief, yes! Anything can be used incorrectly. The 'trick' is understanding what the thing is intended to do and what it's limitations are. Are tuners a 'cure all' in every case? No! But they can certainly make an unsuitable antenna work in a usable way in a lot of cases.
If you have the choice between using a properly tuned antenna system or using a tuner, then use the properly tuned antenna. If you can't properly tune an antenna and you have a tuner, why not? That applies to not just antennas, but any device that has the 'wrong' impedance.
- 'Doc
 

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