Keyboard Shortcuts
Likes
- BITX20
- Messages
Search
Re: End Fed antennas w/ uBITX
#ubitx
Hi Allison, I have been looking at how 9:1 are wound and most of them look like the example you shared, except for one and it kinda matches what I have. I have a twisted trifilar 4 wraps transformer but it's smaller than the example I found at -??I am including a picture, the one on the left is the new 9:1, and the right is the 1:1. And the inductance I didn't measure before is 197uH between posts on the 9:1. Is there an old school way to determine rf impedance with these measurements or does that require specific test equipment? Or am I fussing too much about something that's probably fine anyway? It's new territory.
|
Re: End Fed antennas w/ uBITX
#ubitx
Chuck,
Right on point.? You nicely summarized methods and process of antenna development in an?antenna engineering firm I worked for. Use case, establish what you need the antenna to do.? ?Also try to not succumb to excess added features.? ?The other side of that is no antenna need be forever, so try different things to meet the need. That includes ways to easily to raise and lower antennas. Design/build/evaluate/modify process is a well known engineering procedure to developing a functional product.? To that I add conceive and evaluate candidates as that is where the process is process started.? Its research, look at antennas and? try to understand what they can do in a specific case.? ?Not all candidates pass muster but one may be the diamond.? ?Also failures can evolve to be the niche solution rather than the general. Simplicity,?within the bounds of fitness for the design purpose.?? Always keep in mind the goal.? ?And if all else fails, KISS, then build it well. All to often antennas are a target of magic thinking or outrageous claims.? Substance is measurable, construction quality, material quality, applicability and frugality.? The latter is not "is it cheap" but "is it a good value". Allison |
Re: Raduino Pill
I got some time to build up the power managememt, Si5351 and LCD sections.?
Updates are posted to: www.w3jdr.com |
Re: End Fed antennas w/ uBITX
#ubitx
Indeed it does for many people.
The test method is not as exhaustive as I'd expect but...? 2450/800=3.mumble as a SWR is low enough to be a measurement that can be used at the qualitative level and with a compensating calculation would net quantitative evaluation.? I suspect they wanted to run power through it as a lowly 2500 ohm 2 watt would have done for simple testing. Allison ? |
Re: Spurious RF at beginning of CW transmission in the uBitx
Bob,?
Good work.? There was an earlier fix that tackled the fact that there is no pulldown? for the open contact its used two cross coupled 3904s to short the unpowered line RX+ or TX+. The side effect there are enough big caps that do not discharge fast. I believe the ubitx? fixes site has it, yes it does. Full description there... ![]() |
Re: hacking bitx40 for 20 metre
#bitx40
On top of changing the BPF and the LO, you may have to change the BFO frequency (depending on which new VFO range you pick) and move it to the other edge of the IF pass band filter since 20m ham SSB uses USB.
Thang AA6SV |
Re: End Fed antennas w/ uBITX
#ubitx
Warren Allgyer
Kickoff!
Read the review. Understand it is not an ARRL sanctioned review and was not done by their lab. Understand the efficiency measurement methodology was completely wrong. Other than that the review is fine. The antenna will make contacts. WA8TOD |
Re: Spurious RF at beginning of CW transmission in the uBitx
On Mon, Jul 30, 2018 at 01:39 PM, <n1kw@...> wrote:
Bob N1KW Every since the first BITX we have griped and complained about the 20 ms infamous "BITX Click" that occurs in changing over from receive to transmit and from transmit to receive.? Earlier tests indicated that it was somehow associated with hold-over voltage on capacitors between audio circuits and the balanced modulator.? Is it possible that you have now found, and fixed, that long-standing problem? It appears that I have solved the problem! While analyzing the circuit further, I realized that the large capacitor C52, which is charged during receive, would feed back through R52 and R18 keeping the receive path (Q10, 11, and 12) after the balanced modulator "hot" for a brief period. When the transmit path is activated, the receive side of the circuit is going to remain on for some period of time due to the time constants of C52 and its loads. It is understandable that if both directions of the circuit are on, it could oscillate during that time! To resolve the issue I simply added a diode in series with R52 (cathode toward C52) so that C52 can no longer back feed power to Q10, 11, and 12 upon initiation of transmit state. Now the transmitter output looks perfectly clean on the spectrum analyzer at beginning if TX. Shorting the diode causes the problem to show as before. If this fixes that long-standing problem, then we all owe you a big THANK YOU.? Arv K7HKL _._ |
Re: Gamma-matching antenna tuner
hirosmb
¿ªÔÆÌåÓýYou are right, Allison-san.There should be a possibility of lower spurs on uBitx. Thank you for letting me know it. // hiro, JJ1FXF
|
Re: Gamma-matching antenna tuner
hirosmb
toggle quoted message
Show quoted text
|
Re: The dreaded LSB and USB swap problem again
Dan,
We are using KC8CEC's firmware 1.08 or above along with KC8CEC's uBitx Memory Manager to tweak the calibration settings. If you used the stock firmware to set your calibration you are probably out in no man's land. Mine was so far out I couldn't get control of it until upgraded the firmware and used the memory manager, then it's relatively easy once you figure out that the mystery Master Calibration number in the memory manager doesn't mean anything, you just keep changing it one way or the other from the the base settings until you get the results you want. Others have accomplished calibration by other means that i didn't understand, like the zero beat method which never worked for me. The calibration process is the weak link in the whole uBitx design, we keep adding all these awesome features to the firmware while the Cal process stays broken, IMO. Joel N6ALT |
Re: Gamma-matching antenna tuner
I don't think you will be imprisoned for a long time because of the spurs and the harmonics of the Ubitx unless, as Allison pointed out elsewhere, you use the ssb mode above 20Mhz. Il 31/lug/2018 00:20, "hirosmb" <hirosmb@...> ha scritto:
|
Re: uBitX SSB transmit oscillations on 20m only
#ubitx
No mods yet, Raj. I wanted to make it work without adding mods. I'll check K3. I'll also try a .001ufd capacitor across the mic jack once I find one in my collection.
|
Re: Gamma-matching antenna tuner
hirosmb
¿ªÔÆÌåÓýArv,Thanks for your comment. Yes, as Timothy said, I was completely confused that there would have been a gamma-match manual antenna tuner which could have been placed just after the RF output of rig. All what I want is a manual antenna tuner which also works as a LPF, that is to say, a pi-match antenna tuner. BR, // hiro, JJ1FXF
|
Re: Gamma-matching antenna tuner
hirosmb
¿ªÔÆÌåÓýAllison-san, Thanks a lot for your info. I am checking those presented URLs and a bit surprised with a huge filter using PC case. :) In my understanding, because uBitx uses DDS and so is not likely to produce lower harmonics such as by frequency multiplier, but higher harmonics may occur in most cases. Also I am afraid that the fixed BPF or LPF (such as until 30MHz) may not suppress the second harmonics (14MHz) when emitting 7MHz CW, but hoping that the pi-match antenna tuner may work for this case. // hiro, JJ1FXF
|
Re: End Fed antennas w/ uBITX
#ubitx
Yes you may infer some things and guess and sometimes the type of the transformer. You can grossly guess also the material chemistry of the core. Suppose you have an unknown transformer and you read 50uH at the SO239 and 450uH between the antenna terminals. The ratio is 9:1, 50uH at the SO239 indicates the lowest frequency is around 160m and the core cannot be made of powdered iron. Most likely is ferrite. If you find that there is no dc short at the SO239 and you find around 50uH across the pin of the SO239 and one of the terminal and between the outer of the SO239 and the other terminal you have a 1:1 balun, i.e. a choke which will be fine for all the HF. Now an annedocte. A friend of mine bought for 80 euro from a Ham, a monoband wire antenna with a black box but found difficult to tune. He didn't want to open the black box as he was afraid of breaking it, he paid a lot for it! Well, the inner of the SO239 was not shorted so I excluded it was a 9:1 transformer, I thought the black box contained a 1:1 choke, I mean a quite expensive one. But then I asked to measure the inductance between the inner of the SO239 and the wire and between the outer of the SO239 and the clamp. In both cases it was 0uH!!!..... He paid 80 euro for 20 meters of ordinary unipolar wire and an empty black box!!!! Il 30/lug/2018 20:33, "John Smith via Groups.Io" <johnlinux77=[email protected]> ha scritto: The inductance meter reads 97uH to antenna, and 38uH to ground. The first one I bought that looks like this model and is a 1:1 balun has shielded cable to the toroid and shrink wrapped magnet wire wrapped around it, and looks professional. The inductance readings on the 1:1 balun are 49 and 53uH. This 9:1 unun looks like the typical knock off crap made in the back of a Shenzhen market stall with white shmoo hiding the lies. Are these inductance readings something you expected to see, or way off? |
Re: End Fed antennas w/ uBITX
#ubitx
If you are into placing your radiation pattern exactly where you want it with a big yagi,
toggle quoted message
Show quoted text
then a multiband wire antenna is not for you.? Agreed. But many hams are putting up a wire dipole as best they can fit it on the lot into what trees are available.? The radiation pattern is what it is.? An EFHW at the fundamental can work about as well as the more typical dipole with the same radiation pattern, and is easier to put up for mechanical reasons. As a bonus, in my experience it can work very well as a multiband antenna as well. The many lobes at the harmonics actually are not a negative, the dipole isn't? efficient all directions either.? ?Most of us don't have a rotater for our 80m dipole.? Fundamental or harmonics, I'm primarily concerned that it radiate efficiently. If it happens to have a pipeline into Timbuktu and not LA, I'm fine with that. If you don't like the direction it is pointed, try another band and it's a whole new ball game. Trying to make an EFHW into an efficient multiband antenna can be tough. That's why this thread now has 250+ posts. Rather than kick off another storm of posts here, I'll just suggest you?read the EFHW-8010? review in the March 2016 edition of QST. That review squares well with my experiences of that particular antenna. ? ????? Jerry, KE7ER On Mon, Jul 30, 2018 at 01:44 PM, Chuck, N1KGY wrote: Agreed on both comments.? Pursuit of the "All Band Antenna" is the albatross around the neck of many newer hams, and many OMs as well.? The antenna with the least design compromises tend to cover only one band, i.e. a dipole or a (full sized) 1/4 wavelength vertical.?? Can either of these antennas operate (present a reasonable VSWR, and thus 'take power') on other bands, i.e. the 3rd harmonic?? Certainly.? But if we don't examine the radiation pattern produced by said 'harmonic operation' then the utility of the antenna remains undefined, beyond the anecdotal declarations that such antennas "work" for that operator at his/her installation.? |