Date   
Re: si5351a CLK drive levels in uBITX #ubitx

Jim Sheldon
 

Sort of what I thought Allison I'm going to try it at max for a while and see just what transpires.  I have the SA on and will run rig into a dummy load with the SA pickoff in the line - we'll see what I find as far as harmonics.  Unfortunately my SA is an old GW Instek and I can't get enough span at the normal HF frequencies involved to see all the harmonics at once.  I have to carefully increase the center frequency to see 'em all.  Makes it sort of unscientifice and I'm not sure how well calibrated this thing is. 

Wish I could have afforded a RIGOL or Sigilent but I got this one off ITT Tech when they close a NJ branch for just under $400.  Better than no SA at all - LOL - but sometimes the readings (even though it had a recent calibration sticker on it when I got it) can be suspect.

OK, before sending this, I hooked up the SA and ran a harmonic / garbage scan on it.  Set the TX freq first at 3.5 MHz, output 5 watts (where I normally run it).  Set the Spectrum Analyzer input sensitivity to put the signal from the pick-off so that the fundamental was at 0 dBm on the screen and started looking.  2nd Harmonic 55 dB down, 3rd harmonic 62 dB down and all the others were each slightly better than that so I think everything is still OK.  

With the transmitter keyed at 5 watts out, I ran the analyzer through the freq range up into the VHF range and I didn't see any garbage that wasn't at least 60 + dB down from the fundamental.  Remember though this was with the fundamental at 3.5 MHz.  I'm out of time for right now, but will try and run scans with the TX on the higher bands and look for the "spurs" as well.  

I am pleased though that with the clock drive set to the max available in the software, the sensitivity of the RX has increased enough to make it worthwhile and the Harmonics/Spurs are still within FCC boundaries.  (At least on this particular V4 uBITX).

Jim Sheldon, W0EB



------ Original Message ------
From: "ajparent1/KB1GMX" <kb1gmx@...>
Sent: 7/24/2018 12:30:38 PM
Subject: Re: [BITX20] si5351a CLK drive levels in uBITX #ubitx

I haven't looked at spurs or harmonics related to this save for it makes sense.
The drive is way too low and the sensitivity increase is consistent with drive increase.

If the drive is increased the spurs due to mixer overload should improve, harmonics
may stay the same.

The problem is even at 8ma drive your barely at 5dbm out out and most of the
mixers have 6db attenuators ahead of them.... So drive is -1dbm.  The mixers
are running starved.

Allison

Re: #ubitx #ubitx-help Not able to set up extension switches using CEC firmware #ubitx #ubitx-help

Daniel Conklin
 

When no button is pressed it is 255, and when the encoder is pressed it is 3, the same as when I press the first switch. The second switch gives me 6 and the third gives me 7.  I verified the resistors with an ohm meter.  Thanks for helping me work through this.
Dan, W2DLC
 

Re: si5351a CLK drive levels in uBITX #ubitx

Don, ND6T
 

I'd never really considered running it other than full output. Since I run my own firmware all of the time, I never bothered to try it at lower levels and have had great results. Measuring with my old HP power meter I get between +3.2 dBm to +3.8 dBm from 3 MHz to 150 MHz. The slight dip near 52 MHz I attribute to the blocking capacitor that I use. The spectrum analyzer shows it as +3.17 dBm on 10 MHz where my power meter shows +3.8 dBm. That pretty much coincides, since the SA is looking at narrow-band energy and the old bolometer power meter is looking at overall energy (including all the harmonics).
This is using just the Si5351 in a signal generator project.
The mixer depends upon the peak voltage to switch those diodes so I wouldn't think that there would be much of a performance change unless the output was dropped appreciably. I see no reason to run the synthesizer at any level other than full throttle. Did anyone find a measurable increase in either receive or transmit birdies?
-Don

End Fed antennas w/ uBITX #ubitx

 

Not trying to start a "antenna war", but I noticed several people on this forum use "End Fed antennas".(Like Allison KB1GMX).  I have also used them with good success.  I feed them with 33' of coax and a 1:64 unun (PD7MAA design).  I have one with a trap (again PD7MAA blog) doing multiple bands.
On QRZ, everytime a End Fed topic is brought up, there is a bunch of nay sayers that always chime in. What are you experiences with them and QRP?  I'd like to know, being limited by an HOA, for antenna structures.
Thanks,
Jim W0CHL

Re: si5351a CLK drive levels in uBITX #ubitx

 

Allison et al :

I am not sure where I got the dBm numbers corresponding to the si5351a level settings, but I found them written in my notebook when I was looking 
back for something else I noted. Yes I certainly didn't take into consideration the attenuators before the mixers, that makes it into a whole different
"ball-game". 

I am currently running the KD8CEC V1.095 beta with a Nextion display tacked on so until Ian releases this code and puts it in GITHUB
I don't have any access to source code to play with the settings myself. I am anxious to see how much this might  improve the sensitivity on the 
higher bands as my uBITX seems very "quiet" on 20m and up. 

From what I remember seeing in the code, it appears that the output level parameter for the clocks gets sent to the si5351a every time that there is a change in frequency.
If this is the case then there is even the option of varying the level according to dial frequency, if that is desirable (i.e. cranking it up so that there is more gain
on the higher frequencies).

Cheers

Michael VE3WMB 

Re: End Fed antennas w/ uBITX #ubitx

Nick VK4PP
 

Hi Jim.
I am using a HyEndFed 80-40-20-15-10m at my QTH. I am happy with it, But don't have anything to compare with...

I have built a portable version, same as you (PD7MAA) for use when I go away in 3 weeks time with my uBitx.

Try it, and if the SWR is good and you make contacts, got with it!

Good luck and 73 Nick VK4PLN

Re: End Fed antennas w/ uBITX #ubitx

Don, ND6T
 

In 1999 I installed an end-fed wire as a temporary antenna to get on the air. An old pine tree stands 120' tall in one corner of the lot. 'Nuthin' more permanent than temporary! Still there, still working the world QRP all bands. 175' of 14 AWG stranded copper fed with a variety of tuners, most often "T" configurations, the poor ground (about 20' of buried wire and two 8' ground rods) is tuned with a series LC network.
Almost as good on individual bands as a high dipole except for noise. Much more noise pickup than my horizontal dipoles at my mountain cabin (over 70' above ground there). The far end of this end-fed is at 100', the near end about 5'. 72, Don

Re: End Fed antennas w/ uBITX #ubitx

John
 

Jim,
I have an end fed 33' w/9:1 in and I've made contacts all over the US and from Europe to Australia with it from here in central Arkansas.  It is by far my favorite and was also the first one I homebrewed.  It definitely receives better than it transmits, but for me the proof is in the logbook.

73s
John W5JXN 

Re: End Fed antennas w/ uBITX #ubitx

Doug W
 

I am using a myantennas.com EFHW-8010P (resonant on 80/40/30/20/17/15/12/10m without a tuner) fed with 50 feet of RG8X.  I stick to less than 5w on my v3 µBITX.  Most of my QSO's are digital with some voice mixed in.  I get a chuckle out of people that say end fed antennas do not work because most of them are just repeating something someone told them and have no actual experience.  As for real world usage of operating QRP on an end fed antenna, so far I have confirmed QSO's with 49 US States (still need HI), all continents except Antarctica, and my DX list is growing all the time.
--
www.bitxmap.com

Re: PCB Artwork hint

Robert Ogburn
 

You dinosaur, me pond scum...
Red Tape, Blue Tape, Black Tape, DIY pads.....6x8 foot tapeups...  Ah, the xxxx old days!

Re: PCB Artwork hint

Robert Ogburn
 

I have been using DipTrace since it was introduced for home projects.  For 'aesthetics' I set the design rules for a generous keep away. 
Paul, I believe the expression is "pride in workmanship".

Re: PCB Artwork hint

Jerry Gaffke
 

Kicad 5.0 is now out with many significant improvements
    http://kicad-pcb.org/blog/2018/07/KiCad-5--a-new-generation/



On Tue, Jul 24, 2018 at 04:20 PM, Robert Ogburn wrote:
I have been using DipTrace since it was introduced for home projects.  For 'aesthetics' I set the design rules for a generous keep away. 
Paul, I believe the expression is "pride in workmanship".

Re: Don't discount the rotary encoder as being at issue

BobS KE0REM <rshick@...>
 

Mike,
I have a brand new UBitx also and it too is inoperable, apparently due to the encoder.  One of my encoder terminals appears to be shorted to ground - hence the really spastic operation of the UBitx.  Same symptoms as yours, I'd bet, so a new rotary encoder is in my future too.  You mentioned purchasing five from DigiKey - can you provide me with the part number you ordered so I can repeat the order?  This appears to be another case of inexpensive (aka cheap?), untested components that have to be replaced to make the transceivers work.
Thanks in advance for your help - I hope the encoder fixes my transceiver as well as it did yours.
73, Bob

Re: End Fed antennas w/ uBITX #ubitx

Tom, wb6b
 

I use a 55 foot end fed 80 through 10 meter antenna. It is designed to be non-resonant. The impedance of the antenna is in the 300 to 600 ohm range so I feed it with a 1 to 9 impedance matching unun. The resonate end feds are usually fed with a 1 to 64 impedance unum. It should be noted with end fed antennas there still has to be counterpoise, very often it is the shield of your coax run providing that. So, it is a good idea to add a common mode choke before your coax enters your shack. In my case I wound 10 turns of coax through a large toroid. I, also, provided a good ground at the shield side of the cable for safety and static buildup. I only work 80m for a local net, so the tradeoff in my case is 55 foot of wire at 80m will have reduced efficiency over a full half wave dipole. But, it is invisible running just under the railing of an upper deck. On WSPR my beacon has been picked up as far as Antartica. 

Re: End Fed antennas w/ uBITX #ubitx

Bo Barry <bobarr@...>
 

I'm HOA bound too and doing well with the practically invisible MyAntennas EFHW with my ubitx and Icom7300. 
I prefer it for the ubitx since its SWR is flatter than my G5RV (I've hidden in the trees). It needs a tuner for sure.
And actually the EFHW outperforms the G5RV.
If your lot is too small for the 80 meter version, shoot a line over one tree (hoping you have one) and hook each end of the antenna to your two eaves and hung high in the middle by the tree. Inverted slanting V. works great. Good luck Bo w4GHV

Re: End Fed antennas w/ uBITX #ubitx

Bo Barry <bobarr@...>
 

John, I had the 9:1 version (but not at a resonant frequency length) and it required a tuner and I wasn't impressed. I've found the 49:1 to work much better. I plan to rewind the 9:1 to make it a true EFHW. Bo w4ghv

Re: End Fed antennas w/ uBITX #ubitx

John
 

Hey Bo,
Since I'm still laid-up and on sick leave due to knee surgery, I have plenty of time to try out new ideas.  Frankly, I bored out of my mind.  I have extremely good luck with the antenna I've built - had it about a year or so - and used it with good results on SSB, FT8, and WSPR.  That being said, I will look into the 49:1 as mentioned here and maybe it will be the latest and greatest for me as well.  It's the building and trying part of the hobby that I like the most (even though it is sometimes the most frustrating), and I am always looking for another interesting project to try.  

73's
John W5JXN

Re: PCB Artwork hint

Tom, wb6b
 

Yes, the days of staring for hours at a light table with six layers of pin registered mylar, at four times actual size. Trying to figure out where to cut and pull up tape and pads to make a design revision. 

Absolutely true genius was demonstrated by many board designers as they, time after time, pulled off the impossible task of adding components and layout changes on an already overpopulated layout.

The allure of electric drafting erasers. Well, that's another topic. 

On a side note, a company I worked for designed their own graphics processor chips. They had layer plots hanging from the walls of a two story room. I was looking at one closely and noticed drawings of Dilbert and crew tucked into some the obscure areas of the top metal layer.

Tom, wb6b

Re: End Fed antennas w/ uBITX #ubitx

Warren Allgyer <allgyer@...>
 

The reason an end fed antenna “works” on multiple bands as indicated by low VSWR is because of high losses introduced by the 9:1 or 49:1 transformer. For non-resonant wires these losses are 90% or more.

The reason such antennas “work” from the standpoint of making contacts is that losing 90% of your power only reduces your signal by a little over one S unit.

The transformer in such antennas does not “match”. It masks the true VSWR. It is a lot like putting whiteout on the X-rays to cure a broken leg.

WA8TOD

Re: Don't discount the rotary encoder as being at issue

Mike aka KC2WVB <rb5363@...>
 

Sure, here it is. One more day and gmail would have erased my order confirmation. I have saved it as a screen shot since eventually others will need it too.

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On Tue, Jul 24, 2018, 8:22 PM BobS KE0REM <rshick@...> wrote:
Mike,
I have a brand new UBitx also and it too is inoperable, apparently due to the encoder.  One of my encoder terminals appears to be shorted to ground - hence the really spastic operation of the UBitx.  Same symptoms as yours, I'd bet, so a new rotary encoder is in my future too.  You mentioned purchasing five from DigiKey - can you provide me with the part number you ordered so I can repeat the order?  This appears to be another case of inexpensive (aka cheap?), untested components that have to be replaced to make the transceivers work.
Thanks in advance for your help - I hope the encoder fixes my transceiver as well as it did yours.
73, Bob