IC-706 MK II ON 70 MHZ !!!!
hershman
Yes the Icom 706 MK II expanded transmit mod works! Now You can transmit
anywhere from 200 HZ to 200 MHZ (including the British 70MHZ band!
I will post the mods in the next couple of days and they work!
Three diodes! (easy)
Cheers Mate, NS1R Steve Hershman
Matthew Haigh
hershman said...
(assuming it actually works OK with a clean TX output). Surely this
would be another great thing to advertise, and help a wavering purchaser
to justify the additional cost over the Alinco?
It would be interesting to see some lab reports on the performance on
70MHz.
73, Matt G7GCR
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Anthony R. Gold
In article <33AB30...@ix.netcom.com>
hers...@ix.netcom.com "hershman" writes:
> Yes the Icom 706 MK II expanded transmit mod works! Now You can transmit
> anywhere from 200 HZ to 200 MHZ (including the British 70MHZ band!
> I will post the mods in the next couple of days and they work!
> Three diodes! (easy)
That sounds very interesting, and yes I did read Gary Fiber
confirming this news and saying that it took just two diodes.
I understand that GM4ZUK's 4m homepage has announced that the 4m band
has been released for amateur use in South Africa, so we may get a
really interesting band there after all. Right now, when the 6m band
opens everyone gets a chance to work dx. When the 4m band opens we
just get a to hear a concert from Radio Gdansk :-(
It is curious that the G4HCL conversion that we were told here by
Geoff GJ4ICD many months ago was all finished never appeared.
Steve, would you also have any information about power output and
spurious emissions with that mod?
If this works well, Icom UK would be well advised to support or even
offer to perform this as factory approved and warrantied. I fear that
they are not that entrepreneurial.
Regards,
--
Tony - G3SKR / W2TG email: tg...@panix.com
Geoff Brown GJ4ICD
hershman wrote:
> Yes the Icom 706 MK II expanded transmit mod works! Now You can
> transmit
> anywhere from 200 HZ to 200 MHZ (including the British 70MHZ band!
> I will post the mods in the next couple of days and they work!
> Three diodes! (easy)
> Cheers Mate, NS1R Steve Hershman
WARNING!!!!!
Icom UK Ltd have issued a mail to all dealers about this!
The radio does not conform to spec if modified and warranty will be
void!!!!!!
Maybe this is because of the internal low pass filters are not tuned for
the frequencies outside the amateur bands...(nasty sproggies!)
BE VERY CAREFUL ABOUT THIS MOD! It may well blow the finals!
Geoff Brown Icom Dealer
hershman
Who cares about the spurs! As long as You transmit at 100 Watts out
and they get your signal on 4 1/2 Meters. This is a "FREEBAND" !
Finally You guys can get a radio that transmits on .200 HZ to 200 MHZ
Continuous. Yes there are spurs outside the "OFFicial" bands but who
cares.
Matthew Haigh
hershman said...
>Geoff Brown GJ4ICD wrote:
<snip mod 706 for 4M>
>> Maybe this is because of the internal low pass filters are not tuned for
>> the frequencies outside the amateur bands...(nasty sproggies!)
>> BE VERY CAREFUL ABOUT THIS MOD! It may well blow the finals!
>> Geoff Brown Icom Dealer
>
>Who cares about the spurs! As long as You transmit at 100 Watts out
>and they get your signal on 4 1/2 Meters. This is a "FREEBAND" !
>Finally You guys can get a radio that transmits on .200 HZ to 200 MHZ
>Continuous. Yes there are spurs outside the "OFFicial" bands but who
>cares.
I think the RA might care if you cause interference to legitimate
users of frequencies outside the amateur bands. I would have thought
the US license had similar rules to the UK one about spurious emissions.
Of course, this is an academic argument until someone connects a 706
to a spectrum analyser (ideally testing a few from different batches).
If it does have signigicant levels of emissions outside the amateur
bands, then you can't legally use it unless you add filtering. If it
doesn't have significant spurious emissions, then as with all mods
it will be a case of taking your chances on it damaging your radio. You
can pay to have your rig fixed, you can't buy back a revoked license!
Geoff Brown GJ4ICD
Michael Gathergood wrote:
> Does the internal ATU work down to 200 Hz?
>
Sri Mike but it doesn't have an internal ATU
:-)
Michael Gathergood
In message <33AD64...@ix.netcom.com>
hershman <hers...@ix.netcom.com> writes:
> Who cares about the spurs! As long as You transmit at 100 Watts out
Suggest you take a close look at FCC 97.307, expecially 97.307 (c),
(d) and (e). The rules here, although worded differently, aim to achieve
the same standards.
> and they get your signal on 4 1/2 Meters. This is a "FREEBAND" !
What on earth is freeband? Nothing in life is free*, even with our new
socialist government :-)
> Finally You guys can get a radio that transmits on .200 HZ to 200 MHZ
> Continuous. Yes there are spurs outside the "OFFicial" bands but who
> cares.
Does the internal ATU work down to 200 Hz?
73
Mike
G4KFK
IO91PK
* except for worthless warranties on amateur radio equipment, which can
be obtained free from a number of dealers.
Michael J Wooding
In article <866430...@LOWE.CO.UK>, Richard McLachlan
<Ric...@LOWE.CO.UK> writes
>> Who cares about the spurs! As long as You transmit at 100 Watts out
>> Continuous. Yes there are spurs outside the "OFFicial" bands but who
>> cares.
What a wonderful attitude - he deserves to be stripped of his licence
for life.
Mike
--
Michael J Wooding G6IQM email: mich...@vhfcomm.co.uk
World Wide Web site http://www.vhfcomm.co.uk
KM Publications, 5 Ware Orchard, Barby, Nr.Rugby, CV23 8UF, UK
Tel: (0)1788 890365 Fax: (0)1788 891883
VHF Communications Magazine - Especially covering VHF, UHF and Microwaves
Graham Ridgeway
In message <f4tSwAA4...@g6iqm.demon.co.uk>
Michael J Wooding <g6...@g6iqm.demon.co.uk> writes:
> In article <866430...@LOWE.CO.UK>, Richard McLachlan
> <Ric...@LOWE.CO.UK> writes
> >> Who cares about the spurs! As long as You transmit at 100 Watts out
> >> and they get your signal on 4 1/2 Meters. This is a "FREEBAND" !
> >> Finally You guys can get a radio that transmits on .200 HZ to 200 MHZ
> >> Continuous. Yes there are spurs outside the "OFFicial" bands but who
> >> cares.
> What a wonderful attitude - he deserves to be stripped of his licence
> for life.
> Mike
Is that the same Richard who used to live in Romford many years ago
(1960's ?) and operate on 160m. His callsign eludes me, but I will remember it.
From memory some people then didn't like the type of signals that
appeared to emanate from somewhere near the Pettits Lane area.
I wonder????????????? Now at Lowes eh !
Graham
G8UYD ex BRS 33673 ex A3712 original QTH Upminster.
--
Graham Ridgeway
g8...@zetnet.co.uk
g8uyd@gb7hvu
SD62 Lancashire
Michael J Wooding
In article <867172...@microvest.demon.co.uk>, "Anthony R. Gold"
<tg...@microvest.demon.co.uk> writes
>> What a wonderful attitude - he deserves to be stripped of his licence
>> for life.
>
>bit unfortunate.
If you are more concerned about to whom my software attributed the
quote, than about the actual contents of my comment, to whom it was
directed their being no doubt, then that is your problem.
Michael Aust
My friends , the Icom 706 Mark II has a Low Pass filter that cuts off
above 56Mhz, which means it looks like a short circuit. If you try to tx
there all 100watts is reflected back to the PA.
Solid state PA's usually don't like transmitting into shorts!!
The LPF cutoff would nned to be raised, one would need to check if
the filtering is still ok for 10meters.
I think there would be a problem.
Most solid state PA's when loaded into a low impedance(short)
along a load line produce larges amount of Ic(Collector Currents)
and when terminated into these bad VSWR's can oscillate and the
low frequency currents can exceed the safe Ib(base current levels)
in the Bipolars and blow up the devices.
Just doing athe diode mod will not do it for ~75Mhz, the LPF
would need to be redone!!
The original 706 had MOSFETS, when the wide band mod was done
hams would tx above the LPF cutoff and the PA's would blow.
In solid state PA design , there are large signal stability plane
mapping circles for SB1 and MP2 input mapping and SB2 and MP1 that show
with the earlier MOSFET devices, that terminating the PA, under drive in
this area would cause the original PA to oscillate and self destruct.
The bipolar PA has the same problem, under the DCIV conditions
of Ic ver IB with RF drive , in this area with the LPF acting as
a short, the PA K < 1 , which means it can oscillate and self
destruct.
How do I know, I have designed PA's for a major RF semiconductor
manufacturer using Bipolars/MOSFETS for many years.
My advice , keep you fingers out of the radio, it a great radio.
Enjoy it!!
73
Mike
hershman wrote:
>
> Geoff Brown GJ4ICD wrote:
> >
> > hershman wrote:
> >
> > > Yes the Icom 706 MK II expanded transmit mod works! Now You can
> > > transmit
> > > anywhere from 200 HZ to 200 MHZ (including the British 70MHZ band!
> > > I will post the mods in the next couple of days and they work!
> > > Three diodes! (easy)
> > > Cheers Mate, NS1R Steve Hershman
> >
> > WARNING!!!!!
> > Icom UK Ltd have issued a mail to all dealers about this!
> > The radio does not conform to spec if modified and warranty will be
> > void!!!!!!
> > Maybe this is because of the internal low pass filters are not tuned for
> > the frequencies outside the amateur bands...(nasty sproggies!)
> > BE VERY CAREFUL ABOUT THIS MOD! It may well blow the finals!
> > Geoff Brown Icom Dealer
>
Michael Aust
Another thing, I wanted to point out we test our RF power devices
for hotspots and use emitter balasting resistors to equalize the
emitter currents for reliability.
Anyway, we test our 100watt RF transistors with a sliding load
tied to 3:1, 4:1, 6:1 VSWR and depending on the emitter balasting
internal resisors between each cell of the RF trasistor, determines
the PAE , power added efficiency, VSWR handling capability, and
survivability under bad VSWR conditions.
When you transmit with the wideband tx mod into the cutoff region of
the LPF, the reflected voltage from the poor VSWR load returns to the
Collector(Drain if MOSFET) and adds to the VCE(Vds for MOSFETS).
Semiconductor devices have limited breakdown voltages.
If the reflected voltage , plus the supply voltage exceeds the
operating voltag, the part can breakdown and destroy itself.
Transmiiting above 56 Mhz is lnot advised, since as you tx from
60-93MHz, the LPF is rotating the reflected wave VSWR voltage phase
angle and vector subtraction and addition of the RF voltages have
minima and maxima values which vary, dependent on the frequency and
phase shift of the LPF in the 706.
The load line transformers are only limited within a certain range,
and and as you tx, the efficiency of the PA drops above 56MHz, causing
more heating among the emitter balasting sites.
We use liquis crystal thermal imaging (SAGE)to see the channel
temperature profile of the devices which has hundreds of small
devices in parallel to form those two poer devices used in your PA.
(FETS) and calculate Theta J for the realiable junction temperature.
Transmitting into bad loads, cause device overheating for Bipolars,
icreased Ib's for Thermal runaway, that is why the new Bipolar PA
has thermal runaway protection. In MOSFET;s, you don't have Thermal
runaway, but have the Breakdown Vbr issues.
The MOSFET PA was much more wideband, but the reflected voltages
caused by poor VSWR;s and not helped by transmitting into the upper
cutoff of the LPF's , cause instabilities and device failures is
common.
THIS IS WHY THERE IS A VSWR SENSE PROTECTION CIRCUIT IB THE &)^,
IF THE VSWR RISES ABOVE 2:1 THE PA IS BACKED OFF IN POWER TO PROTECT
IT!
YOU MAY ASK, HOW COME IT DOESN/T HELP ABOVE 56MHZ, THE VSWR PROTECTION
IS IS NOT FULLY RESPONSIVE FROM 0.2mhz TO 93mhZ inclusive, it was only
made to cover the ham bands!!
That is why, trying to tx out of band can be dangerous, you need to
know the limitations of the VSWR sampler out of band to effectively
protect the PA devices.
If the VSWR sampler is afer the LPF, this is even worse since
the PA won't shutdown and will pump the 100watts into a short!!
Unless your a true designer of Solid State equipment, I would adise
that you keep out of the 706, unless you know really what your
doing, which maybe less than 1% of the hams do, but the discussion
here is to technical enlighten your understandunfg of the issue here
and you you merely tx _75Mhz m without modification of the LPF and
VSWR sense, the PA is at your mercy and may be destroyed.
The 706 is loaded with LPF, for the different HF segments, if you
don;t know the cutoff's as you tx ou of band, then you are puuting you
706 not an ideally intended operation from a semiconductor reliabilty
issue.
The manufacturer only stand by it in-band, out of band, I would say
100% he does not!!
My recommendation, use the rig as is , unmodded, and it is great,
will last for years, Most of you are not RF engineers and without
that understanding, these mods can put undue problems without proper
engineering.
Once modified, Icom warranty is out the door!!
73
Mike
Michael Aust
Matthew Haigh
hershman said...
>Mike is correct. You will destroy the radio if you transmit on 70MHZ.
>I was just trying to get some "action" on this otherwise "mundane"
>Newsgroup. I suggest the mod that opens up the transmit from
>1.6 to 60 MHZ and 135 to 175 MHZ. Anthing else and the radio will
>self occillate and destroy itself and Icom will not cover the repair
>under warranty.
> 73' or CHEERS MATE NS1R Steven Hershman
I can accept that you made a mistake. That can happen to anyone. I can't
accept you posting information that you know to be inaccurate to
get some 'action' in a 'mundane' newsgroup. If you don't like the
group, unsubscribe.
Matt G7GCR
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ismo.l...@gmail.com
> anywhere from 200 HZ to 200 MHZ (including the British 70MHZ band!
> I will post the mods in the next couple of days and they work!
> Three diodes! (easy)
> Cheers Mate, NS1R Steve Hershman