thanks, wayne.
- f
On Fri, Jul 29, 2016 at 9:56 PM, Wayne McFee <nb6m@xxxxxxx> wrote:
Hi Farhan,
It is explained in Part 97, section 307(d).
For any HF transmitter installed after January 1, 2003, the requirement is
-43 dBC regardless of power level.
For transmitters installed on or before 1 January 2003, the old standard
of -40 and -30 for less than 5 Watts output.
Here is a link to the document. Section 307(d) is on page 26 of the 34
pages shown, but labeled 612 at the bottom of the page.
https://www.gpo.gov/fdsys/pkg/CFR-2010-title47-vol5/pdf/CFR-2010-title47-vol5-part97.pdf
Regards,
Wayne
On Jul 29, 2016, at 12:59 AM, Ashhar Farhan <farhanbox@xxxxxxxxx> wrote:
thanks wayne, is there a site or a pdf that clearly mentions this ? there
is a lot of legal mumbo jumbo. i wish that arrl maintains a page with all
the requirements clearly mentioned including frequencies, class of license,
permitted modes, spurios requirements, etc.
- f
On Thu, Jul 28, 2016 at 9:33 PM, Wayne McFee <nb6m@xxxxxxx> wrote:
Farhan,
The US requirement for all power levels was changed to -43 dBC, so the
minus thirty won't work for us.
Wayne
On Jul 27, 2016, at 9:58 PM, Ashhar Farhan <farhanbox@xxxxxxxxx> wrote:
here are some scans of a 'minima' line up using diode mixer with a two
transistor termination insensitive amplifer (same as the HF1). The IF is at
24 MHz and the low pass filter has a cut-off at 21 MHz.
As you can see, it works fairly well with all the spurs well below the
-40dbc level. The QRP levels are actually more relaxed (less than 5 watts,
can make do with -30dbc). Further, the low pass filters of the transmit
side will suppress these even more.
- farhan
On Thu, Jul 28, 2016 at 7:39 AM, allison <ajp166@xxxxxxxxxxx> wrote:
On 07/27/2016 06:31 PM, Joe Rocci wrote:<7mhz_output.png>
Qu of the varicap equals Rp/Xp. Paralleling varicaps halves both, so I
can't see how it improves the unloaded Q. Paralleling coils doesn't help
for the same reason.
Measured says no. The distributed currents are important. However the
Q doesn't double
either. Paralleld Xp is for the unit (pair) but each X and each R are
getting a portion of the
total current. The coil case to get more inductance you use series
not parallel.
Even if we accept the the marginal Q its a means to tune a double or a
triple tuned band pass.
The losses at HF are less problematic as we are not working with a
exotic high performance
receiver or transmitter. Even with loss and low Q it may beat trying to
low pass and trap
the IF. If a mechanical cap (still not the highest Q) were available
it would be better but
then you trade electronic problems with availability and mechanical
ones. No matter
what you vary its going to be a compromise over the active range. I was
shooting for
something that can work (least for one case I actually tried) and can be
built without
space, tools, and treasure that may be unavailable.
For myself I'd grab a bag of latching relays and build band specific
filters. That we know
can work but while its repetitive circuits is not always simple to do
well (or tune up).
One thing with any lossy system, gain is cheap. That and for minima we
are talking about
better not perfect. I do plan to build it and put it on Genesys and PNA
and see,
once I get a moment.
Allison/KB1GMX
Joe
Sent from my Verizon Wireless 4G LTE Tablet
-------- Original message --------
From: allison <ajp166@xxxxxxxxxxx> <ajp166@xxxxxxxxxxx>
Date: 07/27/2016 6:01 PM (GMT-05:00)
To: minima@xxxxxxxxxxxxx
Subject: [minima] Re: for minima project
On 07/27/2016 01:43 PM, Joe Rocci wrote:
I agree in concept, except that varactor Q's are generally not goodJoe,
enough to get low loss in a hi-Q, narrow band filter. Making the
coupling track over several octaves is also tricky. And then there's
the intermod potential, since the voltage on the varactors will be Q
times the input voltage. Problematic for me, but an academic exercise
since I've never actually tried to do it.
that is true the Q's are not so great. However parallel diodes can
improve the Q (their internal resistances
are in parallel).
IMD is a matter of signal levels and managing them. Also choice of
inductance.
I've modelled it and you need to parallel coils when you reach about
10mhz to keep the coil Qs
up but that's a relay (or two). I did try it on a KNQ7A on 40M.
The story there is they use a
VXO so it only tunes maybe 25khz. I dropped in a DDS to cover the band
and found the
double tuned front end (antenna switch>>DTBP>>SA612) was rather
narrow. So I used
a pair of 1n4007 (20PF as varicap) on each coil and tuned it with 1.5V
bias for the low end
and at 6V bias it hit the high end. Instant preselector. Didn't test
the bandwidth but the
RX sensitivity was unchanged. More importantly the killer BC stations
above .200 didn't
show as intermod. I call than simple and good enough.
Matching varicaps is a matter of fixed bias and a AADE LC-II though I've
tested a bunch of
MV109s and they seems to be very close to each other at several
voltages. Also the filter
can be designed to tolerate some mistuning by way of bandwidth at center
frequency.
It can be an approach. Also loss is tolerable if one uses a small
amount of gain.
Allison/Kb1GMX
Joetrying
W3JDR
-----Original Message----- From: allison
Sent: Wednesday, July 27, 2016 1:11 PM
To: minima@xxxxxxxxxxxxx
Subject: [minima] Re: for minima project
On 7/27/16 9:19 AM, Joe Rocci wrote:
AllisonYes that was it single balanced mixed had blow through and inadequate
As I recall, the problem with the original Minima was that the 20 Mhz
IF leakage through the mixer (IF-RF) wasn't sufficient to prevent
unwanted transmit spurious at the IF frequency, and that the simple
2-band lowpass filter at the input didn't have adequate performance
to improve it enough. I don't see any specification in the ADE-1 or
SBL-1 datasheets for IF-RF rejection, but my recollection is that
numerous packaged and home-brew mixer designs were evaluated with no
definitive solution.
balance. The ADE/SBL rejection was typically
around 40db.
If you don't filter and rely on balance then you need at least 50db to
be "legal" and 56db would be suggested for
If rejection on transmit. The secondary problem is even using high q
coils and caps a notch filter is wide enough that
15m abd maybe even 17M performance is questionable.
I think the proper solution for the original minima is a lower IFRight again. At 9mhz a notch filter has a much narrower and lower
frequency (maybe 9 MHz?) and switched bandpass filters at the
front-end. One could use 2 CMOS bus switches and up to eight 2-pole
bandpass filters to accomplish this (I've done it and it works very
nicely). The final product isn't much more complicated than the
2-band minima lowpass approach and can be implemented incrementally,
adding one band filter at a time as desired. I think one could also
consider this as a souped-up BIT-X.
loss. Mixer performance is
NO worse and likely better and the only near band is 10.1 (30M). so a
filter in the 8.5mhz range
works well or move up to 11.5mhz.
The problem of bandpass filters is the implied spec of minima, the
ability to tune a wide segment of HF with
one filter. For receiving it may fly generally for transmitting band
pass filters per band are the safest way to
meet most PTT/FCC specs for spurs and harmonics. It is possible to
cover 1.5-30mhz suing half octave low
pass and combined high pass filters but t will still be 5 or 6 filters
needing to be switched in and out.
An alternate for that is tunable preselector/passband filters. In the
past that meant a big multigang cap or
a rack of moveable slugs in coils with mechanical headaches. I'd
to do it using Varicap doidesvariable
to see if that can fly (allowing for tracking and IMD needs) as
DC is easier than a rack of gears.instruments
Old school idea, newer parts.
Allison/KB1GMX
FWIW, my 2 cents and all that.
Joe
W3JDR
-----Original Message----- From: allison
Sent: Wednesday, July 27, 2016 8:57 AM
To: minima@xxxxxxxxxxxxx
Subject: [minima] Re: for minima project
On 7/26/16 1:54 AM, Ashhar Farhan wrote:
There are many ways to continue with the Minima:MOs switches or a fully balanged mixer works.
First:
If one crosses over to the fulll H-mode mixer, it might solve the
leakage problem. I have been trying to keep the design simple with
the KISS mixer. Our (Joe and Mine) experiments wiht using MOS
switches were encouraging.
Second:DBM is a easy way to get a balanced mixer. RF/IF gain is easy and
The other option is to just go with a diode mixer. I already have a
transceiver like that in the works with Si5351. It is a low-cost
design that works upto to 21 MHz and uses two oscillators for the
BFO and the VFO. A a post-mix amp had to be added between the diode
mixer and the crystal filter to provide decent termination to both
sides as well as overcome the filter loss. This is a pretty simple
design. The BFO and VFO are entirely software controlled. A single
LPF that cuts off at 21 Mhz is all that it takes. I will soon post
the details.
cheap.
Filters are both easy and hard, easy to suggest and without
isor a procedure that
uses easy to acquire gear hard to assure they work as expected. This
highhampered by fear of
making coils.
Also the IF is too magic as crystal filters are scary for most and
thanHF filter being more so.
As it works the 20mhz is not much better for images or wide tuning
inaccessible9, 10 or 11mhz
because there will be some frequency or range that will be
atas its the IF. Also
the lower frequencies its easier to obtain quality crystals.
One solution is a preselection system. The tube radios did this and
areleast one vendor
(Tentec) did that on their early transceivers. Ganged L or ganged C
isa mechanical problem
but with Varicaps I have prototyped this and considered it a possible
approach. Its another
knob but it is less a problem if its a simple pot and can provide a
higher selectivity front end
which helpful in Eu and many places with high power SW broadcast
stations.
Third:capacitance from gate to drain is first order issue. Then the drain
The JFETs as mixers could be trouble as their gate-source and
gate-drain can go into conduction easily. Instead, if we use BS170
or 2N7000 kind of switching MOSFETS it might just work.
source parasitic diode is the next problem.
I did some work trying them using some TI parts (lower gate to dran
capacitance) and it was not as good as
Jfets properly biased. The trick with Jfets is matched for Idss and
gate cutoff (dual parts are good for this
but scarce) and then raise to source to the gate cutoff value. The
problem is its still a single balanced mixer.
The interesting thing is, though Minima itself was not a very
replicable design, it did teach us quite a lot. It is a robust
receiver and it has had a large number of spin-offs.
Its trouble spots were the 20mhz filter, and the first mixer. Both are
easily solved.
I know from prior work I've done that a 16mhz filter is easier to
realize and crystals
had better temperature stability vs band width. Also 16mhz is far
enough from
14 and 18mhz to avoid spurs in ham bands and images.
At HF a wide band RX or TRX is easier with a VHF if (45mhz or higher).
But for monoband or
a limited number of bands single conversion and a if at 6-12mhz makes
for a simple design
with fewer issues with retaining good performance.
Having built many monoband transceivers (160 through 2M SSB) and a few
multiband plus
a large number of receivers for various uses and tuning ranges there
experience. There are
few magic circuits (thought the DDS and SI570 may qualify) the basic
radio is more a matter
of trade offs and choices. This has not changed since the 40s though
the devices to attain
the needed gain have.
Allison/KB1GMX
<3.5mhz_output.png>
<14mhz_exciter.png>
<21Mhz_tx_exciter.png>
