About the 12mhz spur, the trap I believe is not that simple. Please let me know a good design without affecting the 30 and 20m bands. Checking it on my SDR receiver is really very low.

Il 16/set/2019 03:54, "Curt via Groups.Io" <wb8yyy=[email protected]> ha scritto:

Dale

I can speak to v3 and v4 because they are similar in this regard.

First on harmonics an effective solution involves more isolation in the relays selecting the low pass filters. I am using the external board now kitted by N8DAH. It should make your ubitx compliant on 80 to 17 meters, both cw and ssb. CW tends to be okay on these upper bands without a fix, but not ssb or data modes using the ssb math. An alternative scheme is removing the relays and replacing them with Axicom parts. This tends to be more complex work.

The remedy of the ssb spurs on the upper bands is more challenging. Possibly the Axicom relays may help here along with shielded inductors to replace the toroids at the 45 MHz crystal filter. Others add a second 45 Mhz crystal filter, but without others mods this approach doesn't work for me.

I suggest choosing one of these approaches for harmonics, and working the other matter later.

Curt

So, my uBitx is almost finished !

I haven't made some QSO for now, but I tested it like a WSPR beacon and it's OK (6800km of report max).

Here some views of the beast :


--
73's
Adrien F4IJA

Dale

I can speak to v3 and v4 because they are similar in this regard.

First on harmonics an effective solution involves more isolation in the relays selecting the low pass filters. I am using the external board now kitted by N8DAH. It should make your ubitx compliant on 80 to 17 meters, both cw and ssb. CW tends to be okay on these upper bands without a fix, but not ssb or data modes using the ssb math. An alternative scheme is removing the relays and replacing them with Axicom parts. This tends to be more complex work.

The remedy of the ssb spurs on the upper bands is more challenging. Possibly the Axicom relays may help here along with shielded inductors to replace the toroids at the 45 MHz crystal filter. Others add a second 45 Mhz crystal filter, but without others mods this approach doesn't work for me.

I suggest choosing one of these approaches for harmonics, and working the other matter later.

Curt

础濒濒颈蝉辞苍—

Can I ask your advice on a boat anchor project?? Soon I will start refurbishing more and more ?HW 100s & SB 100s. ? I read that only fractions of a white are needed to drive a 6146 amplifier (driving the grid).? It’s a very high input impedance. ? We just learned how to make 1 to 49 baluns easily for End Fed half wave resonant antennas...(fantastic results!)

. would some 1:100 or so ferrite Baluns work well to feed the output of a micro Bitx ?into the final amplifier stage one of these older boat anchor radios??

Gordon KX4Z

On Sep 14, 2019, at 23:48, ajparent1/KB1GMX <kb1gmx@...> wrote:

EXTERNAL EMAIL: Exercise caution with links and attachments.

Farhan,

Still around and busy.

Check out OZ1PIFs work.? I've run one section of that a 4x4 parallel push pull
on 6M to over 200W.? The yabut is you need 28V power at 15A!? At 12V that
doesn't work well.? The up side is to get that power not much drive is needed
and its easy to over drive it 5-6W was enough.? Its remarkably tough as I
haven't fried it.? The IMD is only OK.? However a really good and heavy built
low pass is needed as the first one with #18 air wound coils heated too much,
#14 wire solved that along with 500V metal clamp mica caps.

A pair of IRF510s can do 40-50w easy at 28V with 1-2W of drive.?
Parallel parts are harder as then you have parallel paths for
RF current to balance.? Cheat on the layout it becomes unstable
or poor power out.? Getting them to as high as 70mhz was not all
that hard if you pay attention to input and output impedance
they must be low for stability and reasonable power.

The 8 IRF510s are cheap but the total system is not cheap as you still
need a big heatsink (130mm by 130mm with 40mm fins? and a? fan) , TR
switching that can handle the power, and a package to put it all in.?
Cheap 28 or 48 volt switching? power supplies are not a solution as
often they are way to noisy on receive.

Things to consider 100W at 12V is about the limit using the right parts.
However the relays now have to be good for at least 5A and 100V
at the output and the input they can be fairly light.? With higher power
higher currents and voltage are the expected thing and parts like
#12 wire, 500V silver mica or ATC 800B are the required parts.

High power (more than 20 or so watts) tends to be expensive and
getting a reliable amp is never trivial task.

Allison

Hi Allison, i did get the prebuilt band pass filter from ebay.? Wondering if you have any suggestions to mod the KL-203 as well as how to mod it to be more sensistive to lower power e.g. from softrock <1w; I am able to trigger AM but not via SSB.

OK, staring from a point of experience...

First serious and decent amps in the 100W and up class even if home built will
cost not less that 2-5$/watt.? There are big metal parts and expensive transistors
in many.

Most of the cheap "70W" ebay amps have not been seen as working, for long.?
They are still in need of box, likely a real heatsink (adequately sized), low pass
filters and plenty of spare Mosfets and some do not work at all wall above 20M.?
Caveat emptor.

I have built many of the EB series of amplifiers and they are good stable designs that?
generally perform to the limits of the devices used.? Comments like "CB amps" are
generally meaningless and better avoided.? I have seen those apnotes applied
to CB and some are junk and a few were well done.? Quality is often a builder
thing rather than application.? All of the amp modules require a Low pass filter(s)?
and will be likely switched with relays or mechanically.

One last thing what you put in had better be good as 10x that will reflect
all of the flaws in you signal and more people will hear them and comment.
if that is not clear, garbage in, means garbage out.

The biggest issue for those amps are the transistors for them are scarce and often?
very expensive.? I built them as I already had the devices and last look MRF454s
are over 100$ a pair for real ones.

EB63, basic simple amp, the down side is the diode current alone will be high
and that establishes the bias.? Efficiency when built right is over 50% however
at 160M or over 10M the design is not optimal, that's hard to do over a decade
of frequency range.? However with a good low pass filter and clean input the
result is excellent but the transistors used are costly and it can be intolerent
[unstable] of random substitutions.?

AN762? is a later design that uses a 723 voltage regulator to do a precision bias?
and that is an improvement.??The deal is its excellent and not a simple build
plus the devices are near extinct, unless treasure is expended.? Most will
choke at the cost of the machined copper heat spreader alone.

An779 20W amplifer for a SSB transceiver, excellent amp with good efficiency
and low IMD? output.

AN593 amplifier for 160W (28V use) and a version for 12V that does about 80W
SSB and its a good design but one has to pay attention to the mechanical details
or cooling suffers and for 12V use the power is limited.? Since it has the driver is
part of the design its not suited for more than a fraction of a watt input.? For the
80w (13.8V) version max power in would be around 125mW.? Both versions when
correctly adjusted offer very good IMD.? I've built the 28V version.

Others built include AN791 using MRF247 for 80W at 2m. and the datasheet? MRF492
circuit with bias for 6M and near 100W output.? MRF140 28V 160W amp for 6M,
MRF174 for 2M at 150W, and?a utv8100B amp for 60W (with 5W FT817 drive) at 432.

For VHF and UHF I've built far more but there I do use more power but at HF?
I tend to build to the 4-5W level and rely on either my 100W radio if more is
needed or one of several amps that include the EB63, Wa2EBY,?and a
design that is similar to the EB63 with active bias.


Allison