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Author Topic: FT 101 E Peak Envelope Power MFJ 948 Tuner  (Read 4184 times)
2E0BSS
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Posts: 85




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« on: August 21, 2007, 02:36:38 PM »

I have an interesting question (for me it's interesting) I am licensed as a 2E (intermediate) here in the uk which gives me, on most bands, 50 watts PEP I don't have a stand alone watt meter just one on the SWR meter of my MFJ 948 Versa tuner, however, I'm unsure how to calculate the PEP power when tuning my FT 101 E up. This is how I set power up please correct me if I'm incorrect.

First tune the radio to all the dips and max powers then switch the 948 to PEAK on the meter and lower the power untill it sits just below the 50 watt point in both tuned and bypass just to make sure. The MFJ instruction manual states to the following:

"Peak Power and Average power values are equal with steady unmodulated carriers ie FSK, FM. The PEP is twice the average power with SSB two tone test modulation and may be any amount larger than the average power SSB voice signals"

What does that actually mean as the FT 101 E cannot do FM just AM/CW/SSB.

Any help will be greatly appreciated so I can run the correct power from my FT 101E

Charlotte 2E0BSS
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WB2WIK
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« Reply #1 on: August 21, 2007, 03:03:30 PM »

That's a challenge since the FT101E has absolutely NO power output adjustment of any kind when used on SSB!
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2E0BSS
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Posts: 85




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« Reply #2 on: August 21, 2007, 03:29:51 PM »

Ok that's very interesting so when I adjust the  carrier to lower the power what am I actually lowering ? The power on SWR meter does drop and the reports I get are no different to my 857D on 50 Watts.

I previously was told if I lower the Carrier till the 50 watts or as near as possible to it is lined up with the needle then I'm transmitting around that power I guess that's incorrect info. How can people operate on Top band with them at a lower power level ie over here in the uk it's 32 Watts

Any more advise would be greatly appreciate. Does anyone know where I can get the unit serviced ? mainly in the UK

Thanks Charlotte 2E0BSS
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KE3WD
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Posts: 5689




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« Reply #3 on: August 21, 2007, 05:57:16 PM »

I think what you are doing will "put you in the ballpark".  And after all, it is all that you can do with that meter.  

I also don't think that they expect you to nail the 50WPEP with a calibrated instrument, either!

You could also measure DC Voltage and Amperage at the power supply and multiply by efficiency factor, or even get into that ballpark with the AC mains voltage/current, but again, I think that you are giving it the old college try here.  

But I don't know what the situation is in your country, if you actually have inspectors or the like who will knock on doors demanding to use their equipment to measure your power output, that would be another story entirely.  

Outside, they aren't going to be able to tell all that accurately whether your signal is 40, 50 or 75W PEP at the radio antenna jack.  


KE3WD
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KE3WD
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« Reply #4 on: August 21, 2007, 06:01:27 PM »

>> previously was told if I lower the Carrier till the 50 watts or as near as possible to it is lined up with the needle then I'm transmitting around that power I guess that's incorrect info. How can people operate on Top band with them at a lower power level ie over here in the uk it's 32 Watts <<

If you can't adjust the rig down low enough from the front panel, the thing will have to be modified internally to accomplish this.  

Not all that hard to do, lowering output power is a lot easier than trying to make it higher than the radio is designed to do and will also derate the PA quite a bit, the tubes should last virtually forever.  

Cutting the power in half is likely as easy as inserting a plate voltage dropping resistor in the right place.  There are other ways, of course.  This one is "brute force".  


KE3WD
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KE3WD
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« Reply #5 on: August 21, 2007, 06:16:20 PM »

BTW the Manual for the 101E states, "The operator may select any power output desired by simply rotating the "CARRIER" control within the limits of its range from one to ten".  

Are you saying that with the CAR control all the way CCW, the output power is still too high to meet your requirements?

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W2RDD
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Posts: 191




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« Reply #6 on: August 22, 2007, 03:26:51 AM »

Congratulations on having your intermediate license and for making every effort to be an "honest" operator. Ethical behavior is rare these days.
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N8UZE
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Posts: 1524




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« Reply #7 on: August 22, 2007, 05:31:11 AM »

Use CW mode to tune and check your PEP.  The average and peak are identical on this mode and it is a mode that your radio has.  If the PEP on CW is 50watts, your SSB PEP will not exceed 50 watts either.
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2E0BSS
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Posts: 85




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« Reply #8 on: August 22, 2007, 09:59:29 AM »

today my mic quit on me for my 101E so I'm guessing the problems may have related to it. As for the power issues I've checked the meter against known accuracy set up my 101E accordingly so it's going to be around 50watts.

Now go to find a replacement mic for my 101E. Thinking of the new MFJ one for Yaesu, although it's so new no store can tell me if they work as they haven't sold any.

Yaesu are sending me all the manuals for the radio including the technical supplement so that will be a start.

Charlotte 2E0BSS
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WB2WIK
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« Reply #9 on: August 22, 2007, 02:39:07 PM »

The one mistake in what you're doing is that the CARRIER control has no effect whatever on SSB power.

It adjusts the output in the CW mode from "full" to very low (nearly zero) if you turn it all the way down.

However, go ahead and do that: Turn it ALL THE WAY DOWN, to "zero," and then use SSB.  Your output power will be the same as it was when it was all the way up.

The carrier control does not adjust SSB output power, only CW.

Same goes for the TS-520S and virtually all transceivers from the 1960s through the 1970s, and even a bit into the 1980s.  

WB2WIK/6
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2E0BSS
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« Reply #10 on: August 22, 2007, 03:54:17 PM »

So no matter what my ATU is saying the Radio is still transmitting at around 130 Watts PEP? This is bad news. Is there any way at all including turning the VR's inside to lower the physical power output. I'm still at a loss though because over here in the UK Top Band (160m) has a max of 32Watts how do hams comply with that? I know of hams who use FT 101 series units.
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WB2WIK
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« Reply #11 on: August 23, 2007, 10:14:12 AM »

There are ways to reduce FT-101 power, but turning down the CARRIER control isn't one of them, unless you're on CW.

Of course, MOST DXing on 160m *is* CW, so maybe that explains what they're doing on 160.

To reduce SSB output power, you can use a variable voltage power supply applied to the ALC input contact on the FT-101 rear panel.  This would be a "negative" voltage power supply (+ from the supply would be chassis ground), so it must be isolated.  I've used something as simple as a 9V alkaline battery with a 10K potentiometer wired across it, using the wiper terminal and one end terminal to produce an adjustable external negative ALC voltage from 0 to 9V.  That's usually about sufficient to turn the transmitter power down quite low.

I would NOT recommend making any internal adjustments in the FT-101.

WB2WIK/6

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KE3WD
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Posts: 5689




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« Reply #12 on: August 23, 2007, 07:26:41 PM »

WB2WIK -- Using a pot as voltage divider into the ALC (and the 9V battery) is a great idea!  

shoulda thunk of it.  


KE3WD
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N1UK
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Posts: 1436




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« Reply #13 on: August 25, 2007, 02:02:56 PM »

Can't he just reduce the mike gain? It certainly reduces the power very nicely on my TS930S.

The peak power meter on the MFJ is likely to read low. To get an accurate PEP measurement you need a meter with active circuitry in it. This is a nice one

 
http://www.eham.net/reviews/detail/5691
 
http://www.daiwa-industry.co.jp/radio/ham_e/cn801ehp.htm
 
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K7KBN
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Posts: 2802




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« Reply #14 on: August 25, 2007, 10:02:11 PM »

Don't confuse "PEP" and "peak", people.  Peak power meters are the ones that need the active circuitry and therefore need a power supply (wall wart or internal battery) to run this circuitry.  Many relatively inexpensive meters read average and PEP, but not true peak.  My MFJ-986 tuner says "peak", but it really isn't; it's PEP.
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73
Pat K7KBN
CWO4 USNR Ret.
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