Re: Higher SWR Dummy Loads ??
6 dB attenuator - open and shorted output.
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Re: QMX+ Military Version
That is really nice, Dave!? I wimped out and bought my kit with the case... hoping to start on it this weekend. You definitely will not have anyone claim it is another QMX+ "twinkie".? After I built my K2 a hardcore homebrewer
accused me of building another "twinkie".?
Mike KD5KXF
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The waiting list is scrolling very quick!
Hey Hans,
?
Looking at the , one can be very pleased with the scrolling speed. Your "elves" assemble our much-wanted radios very quickly! We are at the end of February, and they are beginning to assemble the January orders. That's great news—thank you, and keep up the good work!
?
73, Joe, DJ0CHE
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Re: Higher SWR Dummy Loads ??
Been using one since my Novice days.
1975.
Was created not knowing any better because the vaporizer, ya know
the old like hankscraft
vaporizer for when you are sick? And if your water was too "Soft"
no minerals,
and it wouldn't boil in tme manual it told ya to add saly or soda
till it would start to boil.
Think about it, many super high voltage high power tubes use
distilled water as the cooling medium. and were like talking 10
thousand volts in contact with the water.
But pure water just H2O is an incredible insulator.
The Mayo jar if it had pure H2o in it would give over 40 meg ohms
resistance!
Being a stupid teenager ham, I thought what's happening and
figured when addind the soda to the water it is lowering the
resistance and ya know for makong power and all that current draws
etc. bla bla bla. so thats how I made my first one in 1975.
Joe WB9SBD
On 2/27/2025 10:54 AM, Todd W2TEF via
groups.io wrote:
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Show quoted text
Soda/salt water dummy load?!? Why didn't anyone tell me it could be this easy and cheap?
A web-page about the idea:
Thanks for the tip, Joe!
72 de Todd W2TEF
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Re: Recommendations for solder temps and workstation
On Thu, Feb 27, 2025 at 08:08 AM, Dean - KC9REN wrote:
This one addressed both those issues: ?
What is the spare tip situation?? Much of the Chinese stuff uses Hakko tips, if this one does I might look into it.?
?
I am also considering this one, which has the temperature sensor embedded near the tip;? it uses proprietary, but inexpensive, tips.??
iron
shorter tips
73, Don N2VGU
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Re: QMX+ Military Version
On Wed, Feb 26, 2025 at 04:07 PM, Jeff Koenig wrote:
May I ask the name of the font you used for the lettering??
Not the intended recipient, but I use this for my MIL and test equipment builds.?
It is a variation on DIN17, from 1938: ?
The DIN standard, "" has been withdrawn but it is still very usable.
Extremely legible and should be easy to print.
?
73, Don N2VGU
?
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Re: Higher SWR Dummy Loads ??
Soda/salt water dummy load?!? Why didn't anyone tell me it could be this easy and cheap?
A web-page about the idea:
Thanks for the tip, Joe!
72 de Todd W2TEF
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Re: Someone in DL-land depressed by a broken QMX (+)?
#qmx
#QMXp
On Wed, Feb 26, 2025 at 04:02 PM, @Ludwig_DH8WN wrote:
I realized changing a STM32 with 100 pins is more fun then a PCM1804 with only 28 pins.
It is a nice feeling of accomplishment when the part "snaps" perfectly into alignment with the PCB lands, almost like magic.
73, Don N2VGU
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Re: Higher SWR Dummy Loads ??
Many thanks everyone.? Lots to ponder. A couple to try with what I have on hand.
On Thu, Feb 27, 2025 at 11:02 AM, Mehmet Dinch via groups.io <msdinch@...> wrote: I should of added, connect your dummy load to the antenna port of the ATU.
?
Mel. M0KMD.
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Re: iPhone camera adapter, receive but no send?
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Re: Higher SWR Dummy Loads ??
I should of added, connect your dummy load to the antenna port of the ATU.
?
Mel. M0KMD.
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Re: Higher SWR Dummy Loads ??
Hi Greg,
?
How about usin an antenna matching unit. You should be able to set the SWR where ever you want it.
?
Cheers,
?
Mel. M0KMD
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Re: iPhone camera adapter, receive but no send?
Haha! That’s an EFHW I built using a tiny transformer and some 26lb steel fishing line. It’s spooled so I can deploy it quickly and has knots at each band so I know where to clip the pigtail.?
Works pretty great! That day I had about a 1.5-1.6 SWR the entire time I was transmitting.?
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Re: Has anyone built the 10 watt PA kit and used it with the QMX?
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Re: iPhone camera adapter, receive but no send?
What in the world is the yellow chalk box with BNC doing on the table?
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Re: Higher SWR Dummy Loads ??
On 27/02/2025 14:55, Stig oz8pz-oz8wsp-oz8wsr via groups.io wrote: o get a swr 2, just use a T bnc and put 2 dummy load on it, then they will
be in parallel, 25 ohm. The other is to put 2 dummy load in serie, but that is
not so easy, to get 100 ohm. And note that each of those ways will have a different effect on the PA. You could make different SWRs by adding L and C all giving different loading conditions with a SWR of 2.0 73 Alan G4ZFQ.
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Re: Higher SWR Dummy Loads ??
Use 4x3W 100Ohm non-inductive resistors (a series of 2 parallels, or a parallel of 2 series, is the same) soldered on a BNC connector. They can dissipate 12-15W peak, and would not get hot with 4-5W.
?
72/73 de Enzo M0KTZ
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Re: Higher SWR Dummy Loads ??
This is simple, make several soda
water dummy loads.
Here is Mine.
I made mine 1 to 1 SWR. it is dead flat from 160 thru 2 meters.?
Probably Higher, but don't know because don't have equipment any
higher.
1500 watts+ into it with mo problems also.
Costs Nothing.
Made simple, the two wires are 12 ga copper, about 6 inches long.?
Open at the far end.
Simple center conductor goes to one wire, Braid to the other.
Fill jar with water.
Measure SWR. It WILL have a SWR.? If the SWR is what ya want youre
done.
Naturally the impedance will be higher than 50 ohms.
Add tiny amounts of baking soda to the water, make sure it is
fully mixed, even wait a while to ensure it is completely
dissolved. and measure again. the impedance will have dropped.
Keep adding till you get what ya want. only do TINY amounts. it is
very easy to overshoot what you want.
If you do simplay dump out some solution and add plain water to
dilute it some.
simple...
I haven't tested this idea, of making it variable impedance by
varying the amount of water, in the jar, or varying the amount the
wires are inserted into the solution.? I think it might make it
impedance variable?
Joe WB9SBD
On 2/27/2025 8:26 AM, Greg McCain via
groups.io wrote:
toggle quoted message
Show quoted text
I'm hoping the smarter folks here can help me create some
dummy loads with higher SWR's.
I'd like to do some temperature delta measurements without
putting signals on the air since I want to include some high
duty cycle scenarios at the typical 4-5 Watts outputs of my
QMX's and QDX's.
?
I Googled this idea but only got hundreds of hits on the
general topic of SWR.
?
Perhaps SWR's of just 2 and 3.
?
I think I should limit it to those values just because there
is plenty of evidence that even short bursts of TX into very
high SWRs or open loads is a generally bad idea without super
fast protection built into the TX circuit chain.?
?
Thanks in advance,
?
GREG? KI4NVX
?
?
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Re: QMX+ Military Version
Very nice work Dave !
Did you print the whole case or just the front panel attached to a real PRC case?? Looks Great !
Jim WB4ILP?
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Re: Does L502 cause excessive voltages on the QMX finals?
On Thu, Feb 27, 2025, at 06:16 AM, Jerry Gaffke wrote:
My guess is that the LPF does not behave appropriately for either VMCD or CMCD.
Perhaps a hybrid of the two was found to work best given the need to cover so many bands with so few LPF's.
One possible path forward might be to keep the current design for those that want all bands from 160m to 6m,?
but have an alternate build supporting only 6 bands where each LPF can be optimized for the frequency of interest.
?
?
Jerry,
The model you posted does not include the 100pF capacitor across the inductor that acts as a second harmonic trap.
?
I also got different inductance values from Toroids.info for the transformer windings.? If you use the info from that site and do the 3:2 windings for 12-volt operation, there is almost twice the power difference without L502.
?
73
Evan
AC9TU
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Mike Malone
Donald S Brant Jr
Todd W2TEF
Barb WB2CBA
rsmith