[Amps] FCC Denies Expert Linears' Request for Waiver of

Wed Dec 28 22:10:28 EST 2016

Best post this year.

Mark Bitterlich
WA3JPY

p.s. Of course I am sure many will disagree.

----- Original Message ----- 
From: "Jim Thomson" <jim.thom at telus.net>
To: <amps at contesting.com>
Sent: Wednesday, December 28, 2016 9:41 PM
Subject: [Amps] FCC Denies Expert Linears' Request for Waiver of

> Date: Wed, 28 Dec 2016 16:55:39 -0800
> From: Jim Brown <jim at audiosystemsgroup.com>
> To: amps at contesting.com
> Subject: Re: [Amps] FCC Denies Expert Linears' Request for Waiver of
> 15 dBRule
>
> On Wed,12/28/2016 4:26 PM, qrv at kd4e.com wrote:
>> just the freedom to buy what you want to use?
>
> It has NOTHING to do with freedom. One of the FCC's functions is to
> establish the rules of the road for radio and other communications
> mediums, and their function is much like establishing rules of the road
> for our highways. Speed limits and no passing zones are not restrictions
> on our freedoms, they are practical rules that make it safer for citizens.
>
> The 15 dB rule was established at the height of the CB radio boom, and
> was part of an attempt to deal with illegal operation using ham gear. It
> may have outlived its usefulness, and it the petition to change it is
> timely. But ALL amplifier manufacturers have been subject to it and
> designed their products to conform. SPE chose to ignore it, and those
> who have sold these amps in the US are in violation of Federal law.
>
> My personal opinion is that the ham community would be better served by
> allowing commercially made amplifiers to have more gain _IF_ FCC Rules
> were also amended to tighten IMD and keying bandwidth limits on
> transmitted signals and enforced on manufacturers who sell rigs that
> don't meet those Rules. 20 dB would allow a 10W radio like a KX3 or ANAN
> 10e to drive a 1kW amp to full power. 21 dB gets it to 1.25 kW, less
> than 1 dB below legal limit.
>
> 73, Jim K9YC
>
> ##  Whoa.  I thought the 15 db rule was only for  the 12 + 10m bands ???
> IE:   >  24 mhz.    Below 24 mhz, I was sure that was no gain limit.
>
> ##  spe  et all, would just have to  switch in a pad on the 12+ 10m bands 
> to meet
> fcc compliance.... or increase NFB.
>
> ##  as for the TX  IMD situation, its a mess.   The Z match that the amp 
> makers has chosen, is done
> so  the eff is max, like typ 50%.... but only when the devices are run 
> flat out.... whereby the amp then
> becomes an IMD  garbage truck.   If you back off on the PO of the amp, its 
> imd improves, BUT the eff
> goes to hell, like down to 30-35%  when run at half rated power.   The fix 
> for the eff...is to use less vdc, when
> using lower power levels, but then the IMD goes to hell.  Lower vdc typ 
> makes the imd worse.
>
> ##  to really do it right would mean to use devices rated for 3-4-5 kw, 
> then operate them at 1.5 kw pep out, then
> design the Z match based on 1.5 kw out.     Then use a power supply, that 
> will handle the 1.5 kw output.   Ditto
> with 1.5 kw LP filters.   No rocket science here folks,  for low imd, and 
> 1.5 kw pep out on ssb,  you either  require
> bigger devices, or more devices ....or both.   Typ you will also get a 1 
> db redux in IMD  for every 1 db in NFB.
> Problem is, with more NFB, drive requirements increase.   3db  of NFB on a 
> Drake L4B means you now require 200
> watts to drive the amp.   6db means u  require 400w of drive.  So the NFB 
> works... provided the device has loads of gain
> to begin with.   IMD can also be reduced a bit by tweaking the bias.... 
> like increasing idle current.  But you can only go so far
> with that method.
>
> ## Dishtronics  2.5 kw output amp, when run at 1.5 kw pep out, still has a 
> lousy  -30 db pep IMD.   If you look at the spec sheets
> for these various  devices, esp the  IMD  vs PO graphs, you will soon see 
> that they have to be severely re-rated to achieve  what I would
> call reasonable IMD....   -40db pep.... or –34 db below one tone of a 2 
> tone signal.
>
> ##  problem is, no countries regs that I can see, regulate IMD for amateur 
> use, its a non regulated free for all.    Even if it was regulated,
> which committee  will pick the numbers ?  All the existing gear would be 
> grandfathered.   Its the higher order IMD that causes the real issues,
> like  IMD- 9-11-13-15-17-19  etc.
>
> ##  You would require 2 x sets of regs,  one for the xcvrs..and another 
> for the amps.  Dirty xcvr driving a clean amp = bad imd.    Clean xcvr
> driving a dirt amp = bad imd.   They both have to be clean.
>
> ##  Too bad the ARRL  etc, cant call a spade a spade, when  doing 
> equipment reviews... esp regarding spectral purity.   yes, nice piece of
> gear for a ham amp  / xcvr... BUT  we cant recommend it due to its lack of 
> spectral purity.....then  dont accept their magazine advertising either,
> until said gear meets ARRL etc, min specs for IMD etc.
>
> ## Ok say no regs.    How about voluntary guidelines.      How about some 
> leadership for a change.   If  ICOM / Kenwood / Yaesu  can build
> FCC  compliant marine gear, that meets ITU / FCC specs... they could 
> easily do the same  for amateur gear.
>
> Jim   VE7RF
>
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