Re: More BS-170s in QCX PA?
it appears to me that the BS170 in the PA are just paralleled. Could one then double up each of these, ie, Parallel 6 of the BS170 for "10w" output?, Nick, These are just switches. In theory one would give the same power as six. Three is the figure Hans reckoned that would take the switching current without getting too hot. More power would mean more supply voltage required but the BS170 is already just about on it's limit. 73 Alan G4ZFQ
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I would like to recommend purchasing a low cost L-C meter to measure your actual values for your various toroids to minimize winding adjustments,? A good inexpensive one, which can be found on EBAY, is the LC-100A. Steven, I purchased one of these and it was very inaccurate. Unless someone has a way of checking the accuracy this would be very confusing, worse than useless! This one said it was 1% but was actually more like 15%, far more than the variations in inductance that have been reported. I do not recommend anyone to buy an inductance meter unless they are able to verify it's accuracy. 73 Alan G4ZFQ
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Re: Power output on 20 meters.
I used the mod by DJ2QV.
He wrote :? Now the Output power was still low and current too high. Further Investigation indicated that
the Class E amplifier is somehow loaded by the path to the RX/TX Switch via capacitor C33.
My Feeling was that at 14 MHz the value of 1nF is a Little too high. Probably too much RF is
coupled to the drain of Q5 and causes some nasty effects here. So I changed C33 to 150 pF
and immediately the current dropped to about 0.6 A and I had much more power.
Optimization of the bandpassfilter inductors and the L4 choke resulted in 30-32 V p-p at 50
Ohm, so about 2.2 to 2.5 Watt. That was also measured with the internal power meter (really
nice function!).
My QCX has 5 Watt output now.
Good luck
73 John PD7MAA
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Re: How hot should that 7805 be?
I suggest, and have done it myself, that since it is very easy to bolt on a home made heat sink (i took the small lid of a peppermints tin) and it is on the edge of the board, it may be a good idea to do this if living in a hot environment, running more than 12V, leaving it on forever, etc.
I'm still trying to figure out what sort of home made heat sink would work for the 3 BS170's as I assume chewing gum or blue tack may make it just hotter... probably Google is my friend to answer that question, maybe there is some type of bonding material that would go between the plastic backs and a metal heat sink.
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Re: Power output on 20 meters.
Hi Dean,
Did you try squeezing / spreading turns on the LPF toroids to optimise the transmit power ?? I gained a watt or so doing that.
Cheers, Glenn VK3YY.
On 10 November 2017 at 14:02, K5DH <k5dh@...> wrote: As built, my 20m QCX put out just over 1 Watt, increasing to 1.6 Watts after a few seconds of key-down.? This is with +13.6 VDC from my Astron power supply.? After reading this thread, I replaced the two caps in the LPF with 390 pF, 500 V, 5 % mica caps, and removed a single turn from L2 and L3.? Output power increased to a solid 2.5 Watts regardless of key-down time.? That's plenty of power to make contacts with, but it's still considerably lower than the 4 Watts that other builders are getting.? I can live with it, but I feel like there's more to be had and something still isn't quite right.? Thoughts??
73/72,
Dean K5DH
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Re: Power output on 20 meters.
As built, my 20m QCX put out just over 1 Watt, increasing to 1.6 Watts after a few seconds of key-down.? This is with +13.6 VDC from my Astron power supply.? After reading this thread, I replaced the two caps in the LPF with 390 pF, 500 V, 5 % mica caps, and removed a single turn from L2 and L3.? Output power increased to a solid 2.5 Watts regardless of key-down time.? That's plenty of power to make contacts with, but it's still considerably lower than the 4 Watts that other builders are getting.? I can live with it, but I feel like there's more to be had and something still isn't quite right.? Thoughts??
73/72,
Dean K5DH
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Re: How hot should that 7805 be?
the 7805 is a 5V voltage
regulator. The higher the supply voltage the more heat (energy, voltage,
temperature) the regulator has to dissipate.
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November
9, 2017 at 8:00 PM Actually, I'm going to reply to
my own post... the 7805 gets hotter when I add the GPS unit, the QLG1
to the system...?
Barry
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Re: How hot should that 7805 be?
Actually, I'm going to reply to my own post... the 7805 gets hotter when I add the GPS unit, the QLG1 to the system...??
Barry
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How hot should that 7805 be?
Hello.
I'm running a QCX (firmware 1.00b)? ?from a 12V battery.? ? The heat sink on the 7805 gets hot to the touch...? is that normal?
I wasn't transmitting, just setting the QCX up.? How hot should that component be??
Thanks
Barry? VE3ZLB
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Hi Everyone.
I am new to all this, So please excuse my ignorance. but looking at the schematic, it appears to me that the BS170 in the PA are just paralleled. Could one then double up each of these, ie, Parallel 6 of the BS170 for "10w" output?, never mind how to fit them, just can it be done, from and electronics point of view... and maybe adjust the capacitor for the added capacitance added by the BS170 gates?
73 Nick VK4PLN
?
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I have the LC100-A with the buttons on the right and it always reads high.
It seems to be a different design than the LC100A that has the 4 buttons on the left of the front of the board, which has good reviews...
de va3rr
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Folks, as there is a lot of discussion on toroid winding etc, I would like to recommend purchasing a low cost L-C meter to measure your actual values for your various toroids to minimize winding adjustments,? A good inexpensive one, which can be found on EBAY, is the LC-100A. Search EBAY for "Digital LC-100A high precision inductance/capacitance L/C meter tester".? They go for about $15-16.? It works quite well, but it is not mounted in a case.? If you spend more money, I would recommend the LC-200a. Search EBAY for "LC200A inductance inductor capacitance capacitor L/C multimeter Meter Tester"That one costs about $30 comes mounted in a case,? I own both and they both work very well. I have found after designing and testing many toroid-based filters that inductance values can stray considerably from theoretical value based on number of turns.? Some precautions with these:
?
?Zero (calibrate) just before measurement.? Calibrate often for multiple measurements such as for L or C matching
Increasing Inaccuracy for low inductance values (<~500nH) and low capacitance values (~10pF) due to low measurement frequency ~ 750KHz
?Be careful in accepting inductance values of coils with frequency-dependent (and amplitude dependent) permeability, such as most ferrites.
?Measures effective inductance, not actual inductance,? where distributed capacitance is significant.
?
I have found, in general that inductance values tend to be on the high side for toroids used in HF filters, compared to theoretical values based on number of turns.? I also found that small inductance values (500 nanohenries or less)? using relatively few turns and low permeability material, tend to be way off due to leakage inductance and really need to be measured to get them right.? These meters are also good for verifying no mislabeled capacitors.
?For best accuracy when measuring low inductance devices, do not use flexible test leads
?You can measure test frequency by pushing the rightmost button (depending on version of software used)
? ?
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On Thu, 2017-11-09 at 19:35 +0100, Henning Weddig via Groups.Io wrote: What I can see from the pictures is:
1. the leads to the caps are very long giving an extra L -- so pleqase
keep the leads of the coils and caps short! Those are the components that will be going into my 30m QCX, so no, I'm not going to cut leads short until they are in their final positions on the PCB. 2. measure the return loss of the filter i.e. terminate the filter
with a good known 50 ohm termination, and use a directional coupler
(e.g. Mini Cirucutis ZFDC-20-3) "reversed" i.e. in to the input of the
fitler, out to the tracking generator and connect the coupled port ton
the input of Your NWA, -20 dB is in my example full reflection, -40 dB
is -20 dB return loss.. If you have access to that equipment and want to do those things feel free. I don't have them so no, I won't be doing those things. If the filter is calculated to be Chebychev filter You should see
return lossminima in the passband.
At least do a recalculation of Your filter using e.g. ELSIE! If you want to do that, feel free..... PeterO G0DZB
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Re: 40m - too much gain of whole RX chain
I have a real simple AGC circuit that works perfectly with this kit. ?Im on vacation this week but will publish it when i return to my office next week. It uses a transistor and diode charge pump to control the gate of a fet for variable gain in the audio chain. ?By changing the charge capacitor or the parallel resistor you can make it variable anywhere in the fast to slow range.?
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it:
email:??bill@... ?
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On Nov 9, 2017, at 5:08 AM, ondrej.briatka@... wrote: I built 40m version QCX. It Works fine, I was surprised how this simple radio clear recieve.
But as radio has no AGC, I need use a volume knob a lot. I kept it most of the time almost on zero. The total gain is just too much for 40m (or 80m), I believe optimal for higher bands.
As a 'secure' solution I modified R37 from 1 K to 10K that decrease gain by 20dB. I kept R38 and C23 as it defines cutoff frequency (1326 Hz) for low pass filter.
It works fine, maybe sidetone is quiter. But I am still thinking how to lower gain on first stage IC5.
I cannot touch 100 ohm resistors R5-R9 (input impedance of amplifier) as they are tighten with quad. sampling detector. What about R7-C4, R10-C7 in feedback?
2k2+47n, gain -13dB
3k3+30n, gain -9.7dB
cutoff freq. remains the same
What do you think? Could it affect IP3 / sensitivity of whole in negative way?
73
Ondrej OM4DW
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Re: U3S-19 in the air...struggling for altitude
Looking good!? I switched over to 30m WSPR/JT9 for now, before US3-19 runs out of sunlight this late afternoon; think I'll leave it parked there tomorrow and see if I get any spots.? I had added some more wire length a couple weeks ago and got the wire elevated a bit more, tunes up beautifully on 30m.
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QRP Labs November newsletter
Hi all
For those of you who are not subscribed to the email so didn't see it: QRP Labs November newsletter is out, see the online version at??
Topics:
1. QCX CW transceiver: Serial number passes 2000; shipment updates 2. QCX CW transceiver: Firmware updates 3. QCX CW transceiver: Modifications? 4. QCX CW transceiver: Builder's gallery 5. QCX CW transceiver: YouTube videos, QRP Labs YouTube channel 6. QCX CW transceiver: German and Japanese manual translations 7. QRP Labs at UK National Hamfest 2017 in Newark 8. QRP Labs features in ICQ Podcast episode 252 9. YOTA buildathon QCX construction on the front cover of SPRAT magasine 10. Canadian C3 expedition, tracked by U3S, is complete - and a huge success! 11. Balloon flights 12. Social media, Feedback, unsubscribing
73 Hans G0UPL
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What I can see from the pictures is:
1. the leads to the caps are very long giving an extra L -- so
pleqase keep the leads of the coils and caps short!
2. measure the return loss of the filter i.e. terminate the
filter with a good known 50 ohm termination, and use a directional
coupler (e.g. Mini Cirucutis ZFDC-20-3) "reversed" i.e. in to the
input of the fitler, out to the tracking generator and connect the
coupled port ton the input of Your NWA, -20 dB is in my example
full reflection, -40 dB is -20 dB return loss..
If the filter is calculated to be Chebychev filter You should see
return lossminima in the passband.
At least do a recalculation of Your filter using e.g. ELSIE!
Henning Wedig
DK5LV?
Am 09.11.2017 um 18:55 schrieb Arv
Evans:
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Show quoted text
Peter?
G0DZB
To
add to your analysis, you can add a separate 1-turn link to
your toroid
and
run a small amount of current through it to alter the
permeability and
thus
the inductance.? This is an alternative to changing the
distributed
capacitance
factor.?
In
toroid circuits that have current flowing through the inductor
this current
may
be affecting the apparent inductance by changing core
permeability.
More
turns with current going through them will increase the
permeability
effect.
Arv?
K7HKL
_._
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Re: QCX 7mhz Output Filter
Alan,
Most of my experiments with Class E have been with the Scopematch designed by M0BMU. As with other kits produced by Hans it is best to build it as per instructions and then investigate if it turns out not to do what is expected.
Regarding the specific matter of estimating efficiency at various frequencies by observing the PSU current, I do not have enough experience to comment.
73 John F5VLF PS sorry for the delay in replying, but we have had substantial building works in the house and this has slowed everything down
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-------- Forwarded Message --------
> For an HF linear I was advised many years ago by G2DAF to tune for a
> peak in screen current.
> Class E is not linear and you tune for the correct load impedance - not
> for maximum output.
John
Ah!
So should Julian just leave it as it is or is there a simple way to check?
I assume therefore that should Julian monitor the PSU current it will
show lower efficiency at 7.9MHz?
Julian,
When you made your power output chart was that after the LPF?
((You did say "Next step is to try what Daniel suggested Another test
worth trying is to put the load before the LPF (disconnected) to see
which frequency has the highest output, adjust L4". Which could give
misleading results unless you ONLY measure the 7MHz component, not with
all the possible harmonics.))
73 Alan G4ZFQ
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Hey guys, ? When I measure RF output using the internal watt meter, I get 3.3 watts. The rig was loaded into a dummy load. ? When I use my mobile antenna (SWR 1:8/9) I only get 0.15 watts. I know 1:9 isn¡¯t great but that¡¯s quite a difference. ? Does the dummy load and antenna look differently to the rig? ? I have the 17m version of QCX. ? ? Sent from for Windows 10 ?
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Peter? G0DZB
To add to your analysis, you can add a separate 1-turn link to your toroid
and run a small amount of current through it to alter the permeability and
thus the inductance.? This is an alternative to changing the distributed
capacitance factor.?
In toroid circuits that have current flowing through the inductor this current
may be affecting the apparent inductance by changing core permeability.
More turns with current going through them will increase the permeability
effect.
Arv? K7HKL
_._
On Thu, Nov 9, 2017 at 10:46 AM, G0DZB <g0dzb@...> wrote: On Thu, 2017-11-09 at 14:50 +0000, Alan G4ZFQ wrote:
> > Red plots are wide spaced and green plots are tight spaced.
> >
>
> Peter,
>
> Recently someone pointed out that the inductance does not change much,
> it is the distributed capacitance that makes it look as if it does.
> (Which would also mean that most, if not all, inductance meters do not
> actually measure the inductance in isolation.)
The micrometals web site
has this to say on the subject:
"The cores are manufactured to the AL values listed; the permeability
for each material is for reference only. Toroidal cores are tested with
an evenly-spaced full single-layer winding in order to minimize leakage
effects. Iron powder cores tested with a small number of turns which are
not evenly distributed will produce higher inductance readings than
expected."
It says higher than expected, but is that just because of the change in
distributed C or is there a real change in L ?? It's hard to tell when
all you can easily observe is 1/2¦Ð¡Ì(LC) :-)
> But you have shown how much the spacing might matter if the cutoff
> frequency is close to the top of a band.
I think that is the key thing to draw from these experiments.
> Your wide-spaced ones look about the recommended spacing, except not
> quite as even as the finished product would be.
> I wonder how much extra capacitance squeezing together adds? I would not
> think it to be much, what happens if say 5-10pF were put across the
> inductors?
I'm not sure if the changing distributed capacitance or the changing
inductance is the dominant effect, but at the very least I now have
suitable coils wound for my 30m filter :-)
PeterO
G0DZB
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John PD7MAA
Glenn S
Nick VK4PP
va3rr
J68HZ
Jeff KP3FT