[Moon] Moon Digest, Vol 14, Issue 17, FT-857 power spikes
Chuck Smallhouse
w7cs at theriver.com
Sat Dec 15 23:41:00 CET 2007
Two items of note :
1.) The FT-857 has a 5th wire in the DC connector cable, I don't
recall what the color is, but not black or red. When this wire is
grounded, the 857 goes into the QRP mode. I think that the maximum
power out on HF is about 20 watts. I never measured it on 2M. This
might be a solution to look into or to pose before the Yaesu (FT-857) forum.
2.) I use an IC-706 (50W on 2M) when mobile to drive my TE Systems
400W 2M P.A.. I reduce the 706's output to approximately 20-25
watts by inserting a 3-4 dB attenuator made of a length of the small
RG-141 coax, which has quite a bit of loss at 2M. I mount (stuff) it
into a small box (plastic, bakelight or metal) with "in" and "out" RF
connectors on it. I simply insert it betwen the 706's output and the
TE's input. The built in Rx preamp in the TE more than makes up for
the 3-4 dB loss.
This provides a no muss, no fuss, no spike, solution. No Rx/Tx
switching or "oh heck" I forgot to turn down the power,
problems. Since the 2M output connector on the 857 is dedicated to
VHF/UHF, this coax attenuator doesn't affect full power operations on HF.
Chuck, W7CS
At 04:00 AM 12/15/2007, moon-request at moonbounce.info wrote:
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>Today's Topics:
>
> 1. Two-meter power spikes ruining TE Amplifiers?
> (Cristofori Concerts)
> 2. Re: [Moon-net] Two-meter power spikes ruining TE Amplifiers?
> (Per Sj?lander)
> 3. Re: Two-meter power spikes ruining TE Amplifiers? (W3cmp at aol.com)
> 4. Re: Two-meter power spikes, T E Amplifiers: Thank you
> (Cristofori Concerts)
>
>
>----------------------------------------------------------------------
>
>Message: 1
>Date: Fri, 14 Dec 2007 06:22:15 -0800 (PST)
>From: Cristofori Concerts <kc3re at yahoo.com>
>Subject: [Moon] Two-meter power spikes ruining TE Amplifiers?
>To: moon-net at list-serv.davidv.net, moon at moonbounce.info
>Message-ID: <213692.60800.qm at web51305.mail.re2.yahoo.com>
>Content-Type: text/plain; charset=iso-8859-1
>
>I wonder if anyone has nad experience with this question? I have
>ordered a new TE Systems 400 watt (c. 20 watts in,) amplifier to use
>with my FT-857, and just picked the following post on the FT-857 board:
>
>"Don't know about final bias on 2m and the -857, but apparently this
>radio
>really puts out a power spike when keyed up on 2m, far above rf pwr out
>setting. Seems the rf pwr out is alc controlled, etc.. Not a big deal
>unless
>you're using an amp at max input limits. I understand the TE Sys amps
>sometimes get taken out by such a spike, and not just fm -857's."
>
>Many thanks for any advice about how to avoid potentially blowing out
>an expensive new amp.
>
>73,
>
>Martin, KC3RE
>
>
>
>____________________________________________________________________________________
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>------------------------------
>
>Message: 2
>Date: Fri, 14 Dec 2007 16:48:39 +0100
>From: Per Sj?lander <perolof.sjlander at telia.com>
>Subject: Re: [Moon] [Moon-net] Two-meter power spikes ruining TE
> Amplifiers?
>To: "Cristofori Concerts" <kc3re at yahoo.com>,
> <moon-net at list-serv.davidv.net>, <moon at moonbounce.info>
>Message-ID: <005401c83e68$cc608e60$f0817483 at tcad.telia.se>
>Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
>Think this is a most common problem on a lot of radios today and one way
>forward is putting a "fixed" but adjustable ALC input to the radio to adjust
>the output power.
>
>When setting the output level by software in the radio the power is most
>probably controlled by an ALC feedback causing spikes on the output.
>
>The spikes in many cases appear in the start of each cw dash or dot and not
>only when keying up in FM.
>
>
>
>By using a long-term fixed control of the output power also the spectra on
>the transmitted signal will be a lot cleaner both on SSB and CW. Could be
>very nice for your neighbours also if they are not ham's. :-)
>
>
>
>73
>
>/Per SM3JQU
>
>
>
>
>
>----- Original Message -----
>From: "Cristofori Concerts" <kc3re at yahoo.com>
>To: <moon-net at list-serv.davidv.net>; <moon at moonbounce.info>
>Sent: Friday, December 14, 2007 3:22 PM
>Subject: [Moon-net] Two-meter power spikes ruining TE Amplifiers?
>
>
> >I wonder if anyone has nad experience with this question? I have
> > ordered a new TE Systems 400 watt (c. 20 watts in,) amplifier to use
> > with my FT-857, and just picked the following post on the FT-857 board:
> >
> > "Don't know about final bias on 2m and the -857, but apparently this
> > radio
> > really puts out a power spike when keyed up on 2m, far above rf pwr out
> > setting. Seems the rf pwr out is alc controlled, etc.. Not a big deal
> > unless
> > you're using an amp at max input limits. I understand the TE Sys amps
> > sometimes get taken out by such a spike, and not just fm -857's."
> >
> > Many thanks for any advice about how to avoid potentially blowing out
> > an expensive new amp.
> >
> > 73,
> >
> > Martin, KC3RE
> >
> >
> >
> >
> ____________________________________________________________________________________
> > Looking for last minute shopping deals?
> > Find them fast with Yahoo! Search.
> > http://tools.search.yahoo.com/newsearch/category.php?category=shopping
> >
> > _______________________________________________
> > Moon-Net posting and subscription instructions are at
> > http://www.nlsa.com/nets/moon-net-help.html
> >
>
>
>
>
>------------------------------
>
>Message: 3
>Date: Fri, 14 Dec 2007 14:02:16 EST
>From: W3cmp at aol.com
>Subject: Re: [Moon] Two-meter power spikes ruining TE Amplifiers?
>To: kc3re at yahoo.com, moon at moonbounce.info
>Message-ID: <bda.1e81225d.34942d38 at aol.com>
>Content-Type: text/plain; charset="us-ascii"
>
>Martin:
>
> I do have experience with the FT-897 (which has same internal circuitry
>as FT-857).
>There is indeed a full power spike upon trransmitting (CW or SSB) regardless
>of the poser setting on the menu. Chip Margelli provided a procedure for
>fixing the spike on CW on 6 mtrs; it still appears on SSB. I'm not
>sure what the
>exact term is but the internal ALC doesn't throttle back the transmit power
>immediately upon going to transmit. Yaesu might have additional
>fixes for each
>band and mode.
> Another option is to put a resistor pad on the transmit side of the TE
>brick after the input TR relay to calm things down and just raise
>the output on
>the FT-857. 73 Chris Patterson W3CMP
>
>
>
>**************************************See AOL's top rated recipes
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>------------------------------
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>Message: 4
>Date: Fri, 14 Dec 2007 14:26:13 -0800 (PST)
>From: Cristofori Concerts <kc3re at yahoo.com>
>Subject: Re: [Moon] Two-meter power spikes, T E Amplifiers: Thank you
>To: moon-net at list-serv.davidv.net, moon at moonbounce.info
>Message-ID: <142120.65153.qm at web51306.mail.re2.yahoo.com>
>Content-Type: text/plain; charset=iso-8859-1
>
>Thank you to everyone who replied to this question. I have so much
>valuable information and feel much more assured about this.
>
>I also tried to contact both T E Systems and Yaesu. The results:
>
>I had a very good, informative, and lengthy chat with T E Systems.
>They told me that they had indeed had this problem with their six-meter
>amplifiers because of transceiver power spikes up to the 100-watt
>output possibility of six-meter transceivers, even with the output
>power turned down to the amplifier's input limit. However, they said
>that they have no history at all of their two-meter amplifiers being
>taken out by transceiver spikes from two-meter transceivers with power
>appropriately turned down from the 50-watt output capability. They did
>say that they had some failure from overdriving while actually
>transmitting (purposely or absent-mindedly,) but never a reported spike
>failure. They seemed to think that their two-meter amplifier would not
>experience a problem from a spike from a 50-watt transceiver.
>
>I sent an E-Mail to my contact at Yaesu who had helped to correct an
>FT-857 self-oscillation problem on six meters. The E-Mail was deleted
>with no reply. (Caveat emptor!)
>
>Thanks again for all of the help.
>
>73,
>
>Martin, KC3RE
>
>
>
>____________________________________________________________________________________
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>End of Moon Digest, Vol 14, Issue 17
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