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Re: Poor Quality 50 Ohm Load - Where to get accurate ones?
Thank you for this clarification.
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Great Job! I love the device! Wolfgang ------------------------------------------------------------ RFC1925: (3) With sufficient thrust, pigs fly just fine. However, this is not necessarily a good idea. It is hard to be sure where they are going to land, and it could be dangerous sitting under them as they fly overhead. (6a) (corollary). It is always possible to add another level of indirection. (8) It is more complicated than you think. ;-) Am 17.08.20 um 02:48 schrieb Hugen: The load of nanoVNA-H4 is designed according to 6GHz that S11 is better than -30dB. We can guarantee that S11 is better than -40dB at 1GHz. The 51 ohm resistor is matched in the laboratory, and we need to offset the parasitic parameters at high frequencies. |
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Re: Poor Quality 50 Ohm Load - Where to get accurate ones?
Fully agree with Dave. Are you not awaiting a little bit to much from
the NanoVNA? What precision can be expected regarding impedance, levels, noise figures and so on? The FR4 material may not be precise enough to guarantee 100% precise 50 Ohms impedance for the input/ output lines of the NanoVNA itself! Can it really work that precise? Over what frequency range? And in what impedance range will it show the right numbers? Would you really expect similar figures and precision from it than you would expect from HP/Agilent/Keysight/Tektronix/Rohde&Schwarz labor grade measurement equipment that costs 100 times as much or more? Don't get me wrong, it is really a brilliant DIY project that helps me a lot and is very handy tool for me to get a rough idea of what is going on. But I would never expect the NanoVNA being absolute precise as I think it never was target on that and I doubt it could deliver that precise results. It already does almost magic, so let's adjust expectations a little bit for reality. vy 73, Wolfgang, (DG7NEF) Am 17.08.20 um 17:33 schrieb Dr. David Kirkby, Kirkby Microwave Ltd: On Fri, 14 Aug 2020 at 01:52, Glen Jenkins WB4KTF <wb4ktf@...> -- Mit freundlichen Gruessen, ------------------------------------------------------------ Wolfgang Wilde, -o) Email: wwilde@... Nuernberg /\\ wwilde@... _\_v ------------------------------------------------------------ Diskutiere nie mit einem Irren - er zieht dich auf sein Niveau und schl?gt dich mit seiner Erfahrung. Shit happens - ... manchmal bist du Taube, manchmal Denkmal. Das Software Business ist binaer. Du bist eine 1 oder eine 0, lebendig oder tot. Wer nicht innovativ sein will ist t o t. Startup (von Peter Howitts) Das Wissen der Menschheit geh?rt der Welt. So wie Shakespeare oder Aspirin... Startup (von Peter Howitts) Es gibt keine Hindernisse, keine Grenzen. ueberrascht mich, zeigt es mir, bertrefft mich, bertrefft euch selbst. 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However, this is not necessarily a good idea. It is hard to be sure where they are going to land, and it could be dangerous sitting under them as they fly overhead. (6a) (corollary). It is always possible to add another level of indirection. (8) It is more complicated than you think. Mike Cox, I've got a new angle for ya. (BTW- Long-time fan!) Start doing the total sarcasm posts like normal, but change them a bit so you sound like the Iraqi Information Minister. (I miss him.) "There IS no Linux within a hundred miles of any PC!" I just found out that the brain is like a computer. If that's true, then there really aren't any stupid people. Just people running Windows. Sie sind nicht berechtigt, unrechtm??ige Kopien dieser Mail anzufertigen oder zu vertreiben. This software is an abomination in every sense of the word! Run it! Hug it! Feel the power of the Dark Side! 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COMMAND.COM kann nicht angehalten werden - System halted ------------------------------------------------------- Mind your head and keep it simple ! ------------------------------------------------------- H?flichkeit ist wie ein Luftkissen. Es mag nichts drin sein, aber es mildert die St?sse des Lebens. The light at the end of the tunnel might be an oncoming dragon Wenn Personal Firewalls die L?sung sind, will ich das verdammte Problem zur¨¹ck. [Robin S. Socha] Good, Fast, Cheap: Pick any two (you can't have all three). RFC 1925 Stay the patient course. Of little worth is your ire. The network is down. It's not denial! I'm just very selective about the reality I accept. Erst jetzt nachdem du gesehen hast was du geh?rt hast kannst du m?glicherweise die Wahrheit akzeptieren.... Nichts > Was h?ltst Du von Quotes am Ende? echo '@a=(A..Z,a..z," ");$t="a"x16;{for($x=0,$|=$n=30; $n--;){for($l=$t; 1<rand 7;) {substr$l,rand 16,1,$ a[rand@a]}$q=$_="zeluR xuniL ESuS";for($a=$l; $_;){s/.//;$q++ if chop$a eq$&}if($x<=$q){$e=$l;die$ e,$/if($x=$q)==16}} print$t=$e,"\r";redo}'|perl Thought is limitation. Free your mind. -------------------------------------------------------------------- Verglichen mit jedem x-beliebigen Redmonder Betriebssystem-Clone ist Linux geradezu eine leuchtende Perle der Datensicherheit. ------ Frank Rennemann () ----- Trouble springs from idleness, and grievous toil from needless ease. --Benjamin Franklin ----------------------------------------------------------------- "Na sch?n, was sollen wir also tun, wenn wir von irgendwas Lebensgef?hrlichem gebissen werden?" fragte ich. Er sah mich an, als sei ich bescheuert. "Na, was machen Sie dann wohl" sagte er. "Sie sterben. Was denn sonst? 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Already hugged your Internal IT today? Good, Fast, Cheap: Pick any two (you can't have all three). RFC 1925 Heckler & Koch: The original point?n?click interface. S.E.I.F.E.: Synthetic Electronic Individual Fabricated for Exploration MCSE: Microsoft-Compatible Spongiforme Encephalitis Wenn ich eine SuSE-CD an ein Schwein binde und dieses trete, laufen KDE & Co. auch ohne RAM recht schnell. --Robin S. Socha in de.comp.os.unix.linux.newusers-- "Was meinen wir mit offener und transparenter Kommunikation? Offenheit: Wir halten nicht unn?tigerweise Informationen zur¨¹ck! Transparenz: Wir legen unsere Entscheidungswege offen! Ehrlichkeit und Verl??lichkeit: Wir sagen was wir meinen und stehen zu dem Gesagten!" <> "Q: Wie sind Deine ersten Eindr¨¹cke hier? A: Zun?chst f¨¹hlt man sich etwas gehandicapped - Ich komme aus einer funk- tionierenden und zuverl?ssigen Windows NT-Welt [...]" <> "Q: Wie kommst Du mit der Software hier klar? A: Ich benutze Excel bei der Arbeit. [...]" <> If Java had true garbage collection, most programs would delete themselves upon execution. [Robert Sewell] Karneval ist die j?hrliche ?berdosis Abf¨¹hrmittel f¨¹r Spie?er mit chronischer Verstopfung. [Jens Grivolla] Get back there in front of the computer NOW. Christmas can wait. -- Linus "the Grinch" Torvalds, 24 Dec 2000 on linux-kernel Yeah, yeah, it's 7PM Christmas Eve over there, and you're in the middle of your Christmas dinner. You might feel that it's unreasonable of me to ask you to test out my latest crazy idea. How selfish of you. Get back there in front of the computer NOW. Christmas can wait. -- Linus "the Grinch" Torvalds, 24 Dec 2000 on linux-kernel Elektrosmog my ass. Wenn ich mal in's Keyboard beisse, dann wegen den Unmengen an Kaffee, Zigaretten und dem ungesunden Essen, nicht wegen diesem Esoterikschrott. [Jonas Luster] "Du bist ein Dummer Haufen Luserscheisse. Deine Praesenz ekelt mich an, ich muss mich uebergeben, wenn ich nur daran denken, dass Penner wie Du auf das Netz, das ich liebe und heilige losgelassen werden." [Jonas Luster zu Bernd Haug in dasr] "Geh' fort. Geh' ganz weit fort. Paare Dich mit den anderen Wuersten in microsoft.ALL und detebe, verschone mich, uns, diese Newsgruppe von Deine Luserfresse, JETZT!" [Jonas Luster zu Bernd Haug in dasr] "Du bist so scheisse, selbst das benutzerfreundlichste OS hasst Dich, Mikrowellen schalten automatisch auf GRILL, wenn Du vorbeilaeufst, denn selbst unanimierte Gegenstaende wuerden es hassen, wenn Du Dich fortpflanzen koenntest." [Jonas Luster zu Bernd Haug in dasr] BIND geh?rt genauso zum RL wie Fu?ballbundesliga. Die einen haben Premiere abonniert, die anderen de.comp.security.firewall. [Christoph von Nathusius in dasr] "Ich muss weg!" 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I saw a woman wearing a sweatshirt with 'Guess' on it. I said, "Implants?" Why is it that most nudists are people you don't want to see naked? An expert is a person who avoids the small errors as he sweeps on to the grand fallacy. -- Benjamin Stolberg Tech Support: "How may I help you?" Customer: "I'm writing my first email." Tech Support: "Ok, what seems to be the problem?" Customer: "Well I can get the 'a'. But how do I put the circle around it?" All you have to decide is what to do with the time that is given to you -- Gandalf at The Lord of the Rings Yesterday, All those backups seemed a waste of pay. Now my database has gone away. Oh I believe in yesterday. Suddenly, Tere's not half the files there used to be, And there's a milestone hanging over me The system crashed so suddenly. I pushed something wrong What it was I could not say. Now all my data's gone and I long for yesterday-ay-ay-ay. Yesterday, The need for backups seemed so far away. I knew my data was all here to stay, No I believe in yesterday. Nuke Operator (16. Dezember 2003 23:22) LE Big Macke schrieb am 16. Dezember 2003 20:12 > NCC-1701-A zum Bleistift? Der Fileserver - unendliche Weiten... Wir schreiben das Jahr 2004. Dies sind die Abenteuer des Raumschiffs Nterprise, Das mit seiner 400 Mann starken Besatzung f¨¹nf Jahre lang unterwegs ist, um neue Software zu erforschen, neues Sourcen und neue Binaries. Viele Kilobits vom User entfernt, dringt die Nterprise in Verzeichnisse vor, die nie ein Mensch zuvor gesehen hat. USB is for mice, FireWire is for men! Boy, backups sure are a lot faster since I linked /dev/st0 to /dev/null... A computer is like an air conditioner. It stops working when u open windows. Was ist eine blondine mit gef?rbten Haaren? K¨¹nstliche Intelligenz An der Kinokasse h?ngt ein Schild: Sonderpreis! Soldaten nur ein Euro! Geht die blonde Susi hin, legt zehn Euro auf den Tisch und s?uselt err?tend: "Bitte zehn von der Marine ...!?" |
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Re: Can the NanoVNA be used on 75 ohm cables/ antennas --- Part 2 #75 ohm measurements
The software with the vna (mandatory pc to use it)I made naive calculation for software correction of (nanoVNA) bridges at other than balance: Bottom line: math is doable, but reduced sensitivity slope elsewhere and quantization errors work against precision; for > 2:1 impedance ratios, add a transformer. |
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Re: Poor Quality 50 Ohm Load - Where to get accurate ones?
On Fri, 14 Aug 2020 at 01:52, Glen Jenkins WB4KTF <wb4ktf@...>
wrote: The 50 OHM load (SMA-Male) that came with my nanoVNA-H4 measures 51.13+ Do you have a specification in mind? DC resistance doesn¡¯t tell you much, other than it puts an *upper* limit on return loss. As soon as you go up in frequency, the return loss will most probably decrease. If you measure up to 3 GHz, it gives you no idea what it will be like at 6 GHz. Sometimes loads worsen dramatically with frequency, but others, from the same batch will get better. The last I looked, there was nothing in the NanoVNA firmware that properly accounted for the open or short calibration standards. So there are limits to what you accuracy you are going to achieve if you had a really expensive load, as the phase errors will kill you. Dave -- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@... Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom |
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Re: NanoVNA Raspberry Pi 4
#linux
Hi Chackras,
your amazon link leeds to a NanoVNA, not to version V2! -- DH1AKF |
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Re: We started selling SAA2 with N-type RF connector and 4-inch display
On Mon, Aug 17, 2020 at 07:14 AM, <biastee@...> wrote:
@Shirley Dulcey KE1LI fear this would be a rather tiny niche. Yes, APC7 is quite elegant and the gender-less design is neat. Unfortunately, to fully take advantage of this, your DUT probably needs to be APC7 as well. In any case, couldn't you just get two N/SMA->APC7 test cables? I'm not sure there is much to be gained from having APC7 test ports on the device itself. It also seems to me that APC7 is essentially obsolete. I don't think you can even buy a new Keysight VNA with APC7 testports. It is either type N at the low end or (ruggedized) 3.5mm/2.92mm/etc at the higher end. I suppose it is a high-performance/high-cost connector but it is limited to low frequencies (by today's standards), so this puts it into a somewhat awkward spot. On the plus side, if you still want to use it, you might be able to buy used calkits and adapters at quite reasonable prices. There are a lot of other approaches to dealing with non-insertable DUTs. In many cases, this is now a non-issue, if you have a suitable eCal or a modern analyzer that can do unkown-thru calibration (in principle this can be done with any proper 2-port VNA, but you may need to do a normal SOLT calibration first and then do the actual calibration "offline" on a PC). If this is not an option, an adapter removal calibration can probably be done on most 2-port VNAs as well. Or you can use a thru-adapter that has already been characterized. For a simple transmission/reflection measurement that you are likely to make with the NanoVNA, the most reasonable option is probably not to worry too much. The biggest issue with an uncharacterized thru adapter will probably be load-match calibration. But unless you reverse the DUT manually, you cannot correct for load-match error anyway. If you just roughly estimate the electrical length of your thru, you will likely be fine, unless you need to measure S21 phase very accurately or want to characterize a low-loss DUT (say a cable or another adapter), where the loss of the thru becomes relevant. |
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Re: Can the NanoVNA be used on 75 ohm cables/ antennas --- Part 2 #75 ohm measurements
I seem to recall from the distant past, reading instructions for one of the early hobby vna devices about this.
The software with the vna (mandatory pc to use it) could automatically readjust the response. The demonstration was an ssb sideband filter with input and output inpedance of several 100ohms. The initial result seemed to be a poor filter with maximum skirt attenuation of only 20db but after the corrections were applied, was the expected 80+ db. This was at hf of course. What was going on? Can this sort of correction be applied. How do I assess a filter with several hundred ohm in and out impedance, or do I resort to a spectrum analyser with tracking generator ( do not have one) or noise source, which is what I have done in the past. I still have that kit ( does 0-120mhz using a scope for display) for posterity. Is this an opportunity for a firmware ( or saver) addition? Steve L. G7PSZ |
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Re: Poor Quality 50 Ohm Load - Where to get accurate ones?
On Sun, Aug 16, 2020 at 08:47 PM, Roger Need wrote:
Glen ,They may be reasonably priced, but don't count on them being any better. I have the female Rosenberger SMA kit and the load has a DC resistance of 48.82R. When you look at the specs, this should not be surprising, Rosenberger guarantees 32.2dB DC-2GHz and 26.4dB 2-8GHz. 48.82R is >37dB, so there is a good chance it is still in spec (and probably good enough for most purposes). Note that this is typical for a general purpose termination. Don't expect much tighter specifications on anything that is not sold as a calibration standard (and priced accordingly). Typical performance will be better, but unless you have something better to compare it to (not just at DC), you won't really know for sure. A side note: if I correct for the DC resistance, the Rosenberger load is within <-45dB (@3GHz) of the other female SMA load I have (Huber&Suhner 18GHz). This might just be luck and I don't know how good the other load really is (at DC it happens to be almost exactly 50.0R). Still, at lower frequencies, just correcting for DC resistance during calibration (or selecting the load for DC resistance) might actually work quite well. If the reactive component were already dominant at a couple of 100 MHz, there is probably not much chance of meeting the spec at 18GHz... For some random home-made termination (or ebay special) things will be different. Of course, at higher frequencies this will eventually fall apart as well. Unless you know the offset delay as well and have your reference plane set properly, you might actually make things worse. As others have mentioned, measuring the DC resistance acurately is not totally straightforward either. A normal 3.5 digit multimeter may easily be 0.5%+several digits on the resistance range. Something like the 34401A I used should be within +/- 0.02R. A high-quality banana->BNC and a BNC->SMA adapter ended up working fine, but the cheap ones I tried initially didn't give repeatable results (the contact resistance varied wildly). 4-wire is not necessary, just zeroing with a short is fine (and with the good adapters proved not necessary at all). If I had to do this on a regularly, I would probably make a special fixture. But this was just a one-time experiment out of curiosity. |
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Re: We started selling SAA2 with N-type RF connector and 4-inch display
Those N to sma bulkhead items are $10 each on the link you gaveand the N end has 4 leaves for the central connector. Even allowing for two effectively in series, your results seem poor. Admittedly I did not do a challenging test on my repaired sma connector as I have nothing with me to test (away from home) other than the coax loop with the kit.
Nevertheless I am looking forward to getting my 4¡± screen v2 in a metal case with N connectors. |
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Re: We started selling SAA2 with N-type RF connector and 4-inch display
My (so far hapless) attempt to repackage my original 2.8" nanovna with N connectors (and later a 4" display, and still later my 2.8" SAA-2) lead me to purchase these panel-mount bulkhead adapters (SMA-N) on ebay (from a seller LM4871N I've previously had good luck with):
After initial assembly, I found unexpectedly high 15 dB return loss (S11 reflection with a known-good ~40 dB RL N-male load attached). Isolated issue to these adapters (not the male-male SMA adapters used as a go-between). It wasn't a single-unit issue (all five of them have this behavior.) As the cost was very low (about USD 2 each), I didn't have any fixed expectation, but they're not suitable for VNA (presumably calibration would compensate to an extent, but probably at the expense of S11 dynamic range.) Presumably it's either dielectric material, geometry in the adapter, or both, but this means I'm back to the drawing board. |
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Re: O S L on antenna side of a balun / choke with stud terminals?
On Sun, Aug 16, 2020 at 05:38:07PM -0700, Roger Need via groups.io wrote:
That's very interesting, thanks!The puzzle is this:I took an excerpt from a textbook on this subject for you that answers your question. Here is a link...if we split the transmission line at one end and bend the split ends to beHow does this give us charge acceleration when a 90 degree bend in the |
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Re: We started selling SAA2 with N-type RF connector and 4-inch display
On 8/17/20 3:36 AM, Stephen Laurence wrote:
Followup from my previous post....Connector savers are your friend - I confess, though, that $20 in connector savers (or whatever a M-F thru costs) on a $50 instrument makes me wonder. Having a $50 VNA changes the whole mindset |
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Re: Poor Quality 50 Ohm Load - Where to get accurate ones?
On Mon, 17 Aug 2020 at 12:25, Dr. David Kirkby <
drkirkby@...> wrote: On Mon, 17 Aug 2020 at 01:48, Hugen <hugen@...> wrote:What I mean is what VNA (NanoVNA?) and what calibration kit?The load of nanoVNA-H4 is designed according to 6GHz that S11 is betterHow do you measure the return loss? Dave |
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Re: Poor Quality 50 Ohm Load - Where to get accurate ones?
On Mon, 17 Aug 2020 at 01:48, Hugen <hugen@...> wrote:
The load of nanoVNA-H4 is designed according to 6GHz that S11 is betterHow do you measure the return loss? Dave |
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Re: We started selling SAA2 with N-type RF connector and 4-inch display
Followup from my previous post....
I have just crushed my first female sma on my v2. The connector would not go very far so I took it off, before I started tightening the nut) and looked down the hole. The leaves of the female socket were bent over but not completely crushed. I got out my Chinese ¡°microscope¡± and managed to straighten them with the point of a small sewing needle initially, using the eye end for the final nudges. I took pictures of before and after but could not attach them using an Ipad. When I get to a computer, I can post them if anyone is interested. I looped a short between the two ports and did a scan from 2 to 4ghz and the four traces seemed to be what I would expect, suggesting there was no huge transmission irrregulariy on the repaired connector. I shall be very careful in future (and throw away all those sma standards that rotate the pin when tightening up). My 4¡± SAAv2 with n connectors, when it arrives, will have sma adaptors attached and be the main machine. Replacing sma connectors on these devices is not something I want to do very often. How many of us have had to do this to sma connectors, I wonder. Steve L. G7PSZ |
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Re: Performance of my nanovna V2 clone - return loss of port 2 seems much too high ?
Peter Ide-Kostic
Any one with bad return loss on port 2 (less than 20dB) at 1.5 Ghz ?
On Sun, Aug 16, 2020 at 11:18 PM Peter Ide-Kostic via groups.io <on7yi.pik973@...> wrote: Thank you for your reply |
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ANy expansion for nanoVNA-H?
#expansion
I see that nanoVNA-H, on its PCB v3.4, has an expansion port. Are there already examples of use of this port? I would like to use it for a bluetooth interface.
Regards Piero, I0KPT |
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Re: We started selling SAA2 with N-type RF connector and 4-inch display
Dear all,
I have several nanovnas (some lent to friends), a tinysa and a N-connector v2 on its way. I also have a Deepace Kc901s with N-connectors, an ancient (1990¡¯s) home made spectrum analyser to 100mhz with bnc connectors and several lab-standard HP141 and other boatanchors (destined for disposal). Building up a stock of sma interconnectors, sex changers, pigtails etc was not hugely expensive. My N connected devices will probably have permanent sma adapters attached, BUT, when I want a robust setup to survive being dropped, pulled onto the floor by the heavy cables etc, the N-connectors will survive whereas the sma ones will not. I do not want another connector type to rear its head, unless it is a screw terminal which I connect a wire or banana plug to it, but generally it is not suitable for rf! I am happy with what I have got. When out of the house, the Tinysa is mostly going to be a pocket/ portable device with sniffer/ stub aerial, so sma is ideal. Steve L, G7PSZ. |
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Re: We started selling SAA2 with N-type RF connector and 4-inch display
@Shirley Dulcey KE1L
I have seen China-made APC7-to-N adapters going for <USD20 online; i.e. about a third of the nanoVna's cost. You will need a minimum of one cable and two adapters to test a two-port DUT. Yes, I do see your point that adopting the APC7 will double or triple the cost of nanoVna ownership, but what other recourse is available for measuring a DUT with same sex connectors (i.e. non-insertable devices)? @ Jerry Gaffke Prior to my post, APC7 has never been mentioned in this group. :-) So, there's no APC7 camp, not yet! Leong, 9W2LC |
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Re: O S L on antenna side of a balun / choke with stud terminals?
Roger and Jim.
I looked at Roger's png first, and that does explain why a dipole radiates and a transmission line does not. Will dig into Jim's antenna book when I have a chance. Many thanks for the quick answers to a complicated question. Jim wrote: You would have problems in other senses, some of which manifest in what you might call efficiency.A transmission line with an open at the end has zero current and maximum voltage there. A very short dipole would be a minor step away from that case, Seems the impedance into such a short dipole should be very high and the antenna current thus very low. Though Jim used the phrase "for a given radiated power", which complicates things some. Guess I better read that book. Jerry, KE7ER |
Oristo
Dr. David Kirkby, Kirkby Microwave Ltd
Wolfgang Kiefer
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