Re: Problem with eBay seller SV4401A: CAUTION11
#buying
Of course anyone¡¯s experience may vary, but over a period of years I have made purchased dozens of purchases from both AliExpress and Banggood. I have never had any issues with either group.
However my guiding credo is: If a price is too good to be true, it probably is.
(I never buy from commercial vendors selling on eBay.)
Over the many years of having a PayPal account, I have never had to file a dispute with them.
Maybe I have been lucky¡
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Re: Problem with eBay seller SV4401A: CAUTION11
#buying
You are covered when you pay via PayPal.
Lester B Veenstra K1YCM M?YCM W8YCM 6Y6Y W8YCM/6Y 6Y8LV (Reformed USNSG CTM1)
lester@...
452 Stable Ln
Keyser WV 26726 USA
GPS: 39.336826 N 78.982287 W (Google)
GPS: 39.33682 N 78.9823741 W (GPSDO)
Telephones:
Home: +1-304-289-6057
US cell +1-304-790-9192
Jamaica cell: +1-876-456-8898
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Costin R Sent: Wednesday, November 23, 2022 5:26 PM To: [email protected]Subject: Re: [nanovna-users] Problem with eBay seller SV4401A: CAUTION11 #buying Unfortunately, such situations have also appeared on Aliexpress. Fictitious tracking numbers, seen only by them. Shopping in China has become an adventure. The biggest loss I took was 120 USD, but I have an acquaintance who lost more than 1000 USD. She was convinced by the seller to give up the dispute also with fake tracking logs. It's a shame that platforms like Aliexpress and Ebay allow such frauds to happen. ?n joi, 24 nov. 2022 la 00:13, Stuart Landau via groups.io <stuartl73= [email protected]> a scris: I purchased a model SV4401A 8-inch VNA from eBay seller Hui3165 on Oct 24
because their price was much lower than any other supplier. I followed the
tracking on SpeedPAK Standard from China to my home. It was supposed to
have been given to the United States Postal Service for final delivery on
the afternoon of November 4, but never arrived; I was there. I checked with
the postal service and letter carrier the next day and was told that they
never had it.
I contacted the seller immediately but was told that it had been
delivered. On November 6 I opened a case with eBay. On November 11, eBay
said because the tracking said that it had been delivered, they closed the
case. Not only that, but eBay dropped my transaction on my purchase list so
that I could not give negative feedback. I told my bank what had happened
and they stopped payment on my credit card. Hopefully, that will not be
challenged by eBay. The seller no longer lists the VNA.
In the meantime, the seller also showed two other negative feedbacks
describing a similar story to mine. The buyers did not receive their
packages and were left "hanging in the wind" during the same time period. I
believe that the seller had hacked the SpeedPAK tracking. Their tracking
showed an error with the USPS chain of custody. The seller, who currently
has 136 listings has only 48 sales in six months. Their feedback percentage
now is only 71.4% positive and I am unable to leave my negative feedback. I
blame both the seller and eBay for how I have been treated.
Please be aware of this seller, or any other who has a very low price on a
new item, compared to others.
Stuart K6YAZ
Los Angeles, California
|
Re: Problem with eBay seller SV4401A: CAUTION11
#buying
Similar story on AliExpress out of China on a few orders. In this scam the vender would issue a FedEx tracking number that would show delivered, after some time. However, in conversation on line with FEDEX, their records showed the package contained a trivial item (customs declaration on shipment) and that it was delivered to some other address. In my case, all my transactions are paid via PAYPAL. I disputed the charge with PAYPAL, supplying PAYPAL with a transcript of the conversation with the FEDEX agent. Paypal soon agreed with me and imitated a chargeback to AliExpress, giving me the funds again.
Lester B Veenstra K1YCM M?YCM W8YCM 6Y6Y W8YCM/6Y 6Y8LV (Reformed USNSG CTM1)
lester@...
452 Stable Ln
Keyser WV 26726 USA
GPS: 39.336826 N 78.982287 W (Google)
GPS: 39.33682 N 78.9823741 W (GPSDO)
Telephones:
Home: +1-304-289-6057
US cell +1-304-790-9192
Jamaica cell: +1-876-456-8898
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Stuart Landau via groups.io Sent: Wednesday, November 23, 2022 5:13 PM To: [email protected]Subject: [nanovna-users] Problem with eBay seller SV4401A: CAUTION11 #buying I purchased a model SV4401A 8-inch VNA from eBay seller Hui3165 on Oct 24 because their price was much lower than any other supplier. I followed the tracking on SpeedPAK Standard from China to my home. It was supposed to have been given to the United States Postal Service for final delivery on the afternoon of November 4, but never arrived; I was there. I checked with the postal service and letter carrier the next day and was told that they never had it. I contacted the seller immediately but was told that it had been delivered. On November 6 I opened a case with eBay. On November 11, eBay said because the tracking said that it had been delivered, they closed the case. Not only that, but eBay dropped my transaction on my purchase list so that I could not give negative feedback. I told my bank what had happened and they stopped payment on my credit card. Hopefully, that will not be challenged by eBay. The seller no longer lists the VNA. In the meantime, the seller also showed two other negative feedbacks describing a similar story to mine. The buyers did not receive their packages and were left "hanging in the wind" during the same time period. I believe that the seller had hacked the SpeedPAK tracking. Their tracking showed an error with the USPS chain of custody. The seller, who currently has 136 listings has only 48 sales in six months. Their feedback percentage now is only 71.4% positive and I am unable to leave my negative feedback. I blame both the seller and eBay for how I have been treated. Please be aware of this seller, or any other who has a very low price on a new item, compared to others. Stuart K6YAZ Los Angeles, California
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Re: Problem with eBay seller SV4401A: CAUTION11
#buying
I agree, Paypal is UNSCRUPULOUS, disagree?? Read the story about the guy that made a huge buy of 18650 li-ion cells and then got SCREWED by Pay@$#^ because they (Pay@#$^) wanted to hold the payments 6 MONTHS after he had GREAT success selling them. The seller did NOT like that arrangement so he wrote every buyer and told them to ask for their money back, which they did. Pay@#$^ took that one in the shorts.? I NEVER leave any money in Pay@#^ and wish there was an alternative to them.
Mike C.
Sand Mtn GA
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On 11/23/2022 5:37 PM, Costin R wrote: Yes, I think we need to use payment methods that offer protection for
unscrupulous sellers.
And PayPal is a good example.
?n joi, 24 nov. 2022 la 00:33, John<ve3kkqve3kkq@...> a scris:
I realize that this bit of advice is too late, but always buy from the
OFFICIAL vendor.
I had a similar experience with a "really good deal" on a Chinese VHF
mobile radio.
I was very excited to receive my new rig on the projected delivery date...
disappointment soon ensued.
Investigation soon revealed that my rig was indeed delivered... to an
address in Montreal, Quebec, Canada. I lived in Fort Erie, Ontario, Canada
at that time.
I did not have the presence of mind to cancel the card transaction, so I
was out $50, that should have set off alarm bells at the get-go, does now.
I hope you get the card charg cancelled in time.
John
VE7KKQ
On Wed, Nov 23, 2022 at 2:12 PM Stuart Landau via groups.io <stuartl73=
[email protected]> wrote:
I purchased a model SV4401A 8-inch VNA from eBay seller Hui3165 on Oct 24
because their price was much lower than any other supplier. I followed the
tracking on SpeedPAK Standard from China to my home. It was supposed to
have been given to the United States Postal Service for final delivery on
the afternoon of November 4, but never arrived; I was there. I checked with
the postal service and letter carrier the next day and was told that they
never had it.
I contacted the seller immediately but was told that it had been
delivered. On November 6 I opened a case with eBay. On November 11, eBay
said because the tracking said that it had been delivered, they closed the
case. Not only that, but eBay dropped my transaction on my purchase list so
that I could not give negative feedback. I told my bank what had happened
and they stopped payment on my credit card. Hopefully, that will not be
challenged by eBay. The seller no longer lists the VNA.
In the meantime, the seller also showed two other negative feedbacks
describing a similar story to mine. The buyers did not receive their
packages and were left "hanging in the wind" during the same time period. I
believe that the seller had hacked the SpeedPAK tracking. Their tracking
showed an error with the USPS chain of custody. The seller, who currently
has 136 listings has only 48 sales in six months. Their feedback percentage
now is only 71.4% positive and I am unable to leave my negative feedback. I
blame both the seller and eBay for how I have been treated.
Please be aware of this seller, or any other who has a very low price on a
new item, compared to others.
Stuart K6YAZ
Los Angeles, California
|
Re: Problem with eBay seller SV4401A: CAUTION11
#buying
Yes, I think we need to use payment methods that offer protection for
unscrupulous sellers.
And PayPal is a good example.
?n joi, 24 nov. 2022 la 00:33, John <ve3kkqve3kkq@...> a scris:
toggle quoted message
Show quoted text
I realize that this bit of advice is too late, but always buy from the
OFFICIAL vendor.
I had a similar experience with a "really good deal" on a Chinese VHF
mobile radio.
I was very excited to receive my new rig on the projected delivery date...
disappointment soon ensued.
Investigation soon revealed that my rig was indeed delivered... to an
address in Montreal, Quebec, Canada. I lived in Fort Erie, Ontario, Canada
at that time.
I did not have the presence of mind to cancel the card transaction, so I
was out $50, that should have set off alarm bells at the get-go, does now.
I hope you get the card charg cancelled in time.
John
VE7KKQ
On Wed, Nov 23, 2022 at 2:12 PM Stuart Landau via groups.io <stuartl73=
[email protected]> wrote:
I purchased a model SV4401A 8-inch VNA from eBay seller Hui3165 on Oct 24
because their price was much lower than any other supplier. I followed the
tracking on SpeedPAK Standard from China to my home. It was supposed to
have been given to the United States Postal Service for final delivery on
the afternoon of November 4, but never arrived; I was there. I checked with
the postal service and letter carrier the next day and was told that they
never had it.
I contacted the seller immediately but was told that it had been
delivered. On November 6 I opened a case with eBay. On November 11, eBay
said because the tracking said that it had been delivered, they closed the
case. Not only that, but eBay dropped my transaction on my purchase list so
that I could not give negative feedback. I told my bank what had happened
and they stopped payment on my credit card. Hopefully, that will not be
challenged by eBay. The seller no longer lists the VNA.
In the meantime, the seller also showed two other negative feedbacks
describing a similar story to mine. The buyers did not receive their
packages and were left "hanging in the wind" during the same time period. I
believe that the seller had hacked the SpeedPAK tracking. Their tracking
showed an error with the USPS chain of custody. The seller, who currently
has 136 listings has only 48 sales in six months. Their feedback percentage
now is only 71.4% positive and I am unable to leave my negative feedback. I
blame both the seller and eBay for how I have been treated.
Please be aware of this seller, or any other who has a very low price on a
new item, compared to others.
Stuart K6YAZ
Los Angeles, California
|
Re: Problem with eBay seller SV4401A: CAUTION11
#buying
I realize that this bit of advice is too late, but always buy from the OFFICIAL vendor. I had a similar experience with a "really good deal" on a Chinese VHF mobile radio. I was very excited to receive my new rig on the projected delivery date... disappointment soon ensued. Investigation soon revealed that my rig was indeed delivered... to an address in Montreal, Quebec, Canada. I lived in Fort Erie, Ontario, Canada at that time. I did not have the presence of mind to cancel the card transaction, so I was out $50, that should have set off alarm bells at the get-go, does now. I hope you get the card charg cancelled in time. John VE7KKQ On Wed, Nov 23, 2022 at 2:12 PM Stuart Landau via groups.io <stuartl73= [email protected]> wrote: I purchased a model SV4401A 8-inch VNA from eBay seller Hui3165 on Oct 24
because their price was much lower than any other supplier. I followed the
tracking on SpeedPAK Standard from China to my home. It was supposed to
have been given to the United States Postal Service for final delivery on
the afternoon of November 4, but never arrived; I was there. I checked with
the postal service and letter carrier the next day and was told that they
never had it.
I contacted the seller immediately but was told that it had been
delivered. On November 6 I opened a case with eBay. On November 11, eBay
said because the tracking said that it had been delivered, they closed the
case. Not only that, but eBay dropped my transaction on my purchase list so
that I could not give negative feedback. I told my bank what had happened
and they stopped payment on my credit card. Hopefully, that will not be
challenged by eBay. The seller no longer lists the VNA.
In the meantime, the seller also showed two other negative feedbacks
describing a similar story to mine. The buyers did not receive their
packages and were left "hanging in the wind" during the same time period. I
believe that the seller had hacked the SpeedPAK tracking. Their tracking
showed an error with the USPS chain of custody. The seller, who currently
has 136 listings has only 48 sales in six months. Their feedback percentage
now is only 71.4% positive and I am unable to leave my negative feedback. I
blame both the seller and eBay for how I have been treated.
Please be aware of this seller, or any other who has a very low price on a
new item, compared to others.
Stuart K6YAZ
Los Angeles, California
|
Re: Problem with eBay seller SV4401A: CAUTION11
#buying
Unfortunately, such situations have also appeared on Aliexpress. Fictitious tracking numbers, seen only by them. Shopping in China has become an adventure. The biggest loss I took was 120 USD, but I have an acquaintance who lost more than 1000 USD. She was convinced by the seller to give up the dispute also with fake tracking logs. It's a shame that platforms like Aliexpress and Ebay allow such frauds to happen. ?n joi, 24 nov. 2022 la 00:13, Stuart Landau via groups.io <stuartl73= [email protected]> a scris:
I purchased a model SV4401A 8-inch VNA from eBay seller Hui3165 on Oct 24
because their price was much lower than any other supplier. I followed the
tracking on SpeedPAK Standard from China to my home. It was supposed to
have been given to the United States Postal Service for final delivery on
the afternoon of November 4, but never arrived; I was there. I checked with
the postal service and letter carrier the next day and was told that they
never had it.
I contacted the seller immediately but was told that it had been
delivered. On November 6 I opened a case with eBay. On November 11, eBay
said because the tracking said that it had been delivered, they closed the
case. Not only that, but eBay dropped my transaction on my purchase list so
that I could not give negative feedback. I told my bank what had happened
and they stopped payment on my credit card. Hopefully, that will not be
challenged by eBay. The seller no longer lists the VNA.
In the meantime, the seller also showed two other negative feedbacks
describing a similar story to mine. The buyers did not receive their
packages and were left "hanging in the wind" during the same time period. I
believe that the seller had hacked the SpeedPAK tracking. Their tracking
showed an error with the USPS chain of custody. The seller, who currently
has 136 listings has only 48 sales in six months. Their feedback percentage
now is only 71.4% positive and I am unable to leave my negative feedback. I
blame both the seller and eBay for how I have been treated.
Please be aware of this seller, or any other who has a very low price on a
new item, compared to others.
Stuart K6YAZ
Los Angeles, California
|
Problem with eBay seller SV4401A: CAUTION11
#buying
I purchased a model SV4401A 8-inch VNA from eBay seller Hui3165 on Oct 24 because their price was much lower than any other supplier. I followed the tracking on SpeedPAK Standard from China to my home. It was supposed to have been given to the United States Postal Service for final delivery on the afternoon of November 4, but never arrived; I was there. I checked with the postal service and letter carrier the next day and was told that they never had it.
I contacted the seller immediately but was told that it had been delivered. On November 6 I opened a case with eBay. On November 11, eBay said because the tracking said that it had been delivered, they closed the case. Not only that, but eBay dropped my transaction on my purchase list so that I could not give negative feedback. I told my bank what had happened and they stopped payment on my credit card. Hopefully, that will not be challenged by eBay. The seller no longer lists the VNA.
In the meantime, the seller also showed two other negative feedbacks describing a similar story to mine. The buyers did not receive their packages and were left "hanging in the wind" during the same time period. I believe that the seller had hacked the SpeedPAK tracking. Their tracking showed an error with the USPS chain of custody. The seller, who currently has 136 listings has only 48 sales in six months. Their feedback percentage now is only 71.4% positive and I am unable to leave my negative feedback. I blame both the seller and eBay for how I have been treated.
Please be aware of this seller, or any other who has a very low price on a new item, compared to others.
Stuart K6YAZ
Los Angeles, California
|
Re: Determining OCFD total length and split points
#circuit
On 11/23/22 4:28 AM, Barry K3EUI wrote: Just to check ¡ª¡ª
The resonant frequency of any dipole (center fed, OCF, or end-fed) is determined only but the TOTAL length of the wire, and not be WHERE you feed it.
(And maybe how high above ground or other nearby conductors).
Altering the feed point location only changes the input IMPEDANCE.
Center feds are typically 30-80 ohms (depending on height above ground).
OCF I¡¯ve seen at 200 to 600 ohms.
End-feds can be thousands of ohms.
Typically you see 1/3, 2/3 split (45 ft, 90 ft) for a 135 ft long wire, which puts the impedance around 400 ohms.
I think some argue that for a 120-140 ft overall length, based on the harmonics but you can try different locations depending on the BALUN ratio.
I ran some quick NEC models, results attached. The R doesn't change a lot until you get outside, say, 0.3 to 0.7 split point (0.5 in middle). This was a dipole "cut" for 10 MHz resonance. And the resonance point does change (i.e. there's some X as you move off the resonance), but it's not huge (the phase is < 10 degrees). Several plots attached for various ranges of split point
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Re: Determining OCFD total length and split points
#circuit
On 11/23/22 8:53 AM, W0LEV wrote: The OCF set of wires is NOT a balauced (differential mode) source/load!
Why use a balun? A balun is a circuit element intended to transform
differential mode (dipole) to common mode (coax). An RF choke consisting
of multiple turns of coax through an appropriate toroid or a number of
clamp-on ferrites on the coax at the feed point are appropriate, but not a
"balun" as such. The proposed "fixes" will choke common mode currents on
the external surface of the coax shield.
Dave - W?LEV
One might want a transformer (which could serve as a balun or RF choke) on an OCF dipole, because the resistive impedance at resonance is typically quite high, compared to 50 ohms. OTOH, if the feedline is the *right* length and type, maybe it's ok. You need an RF choke (or the functional equivalent) if you don't want your feedline interacting with the antenna. On the other hand, for casual use, you may not care - if the feedline (exterior) radiates, and you make a QSO as a result, it's all good. There's more than one antenna out there that the feedline is an essential part of the radiating structure. Traditionally, folks like to prevent the feedline from radiating because: 1) it can be unpredictable - it's hard to know if the system is working with simple instrumentation. 2) it can cause RFI and safety problems due to proximity (feedlines are close to people and victim equipment) 3) it can result in increased losses - imagine a radiating field line immersed in vegetation, the vegetation gets warm, and the power doing that isn't radiating. 4) the interaction of the field from the feedline and the field from the dipole (off center or not) can cause nulls and lobes. That can be good (lobe in good direction, null in noise source direction) or bad (null in the direction you want to communicate) 5) a variant of 4, if your feedline radiates, it also receives, and if you have a noise maker next to the feedline, that can be a problem
|
Re: Determining OCFD total length and split points
#circuit
The OCF set of wires is NOT a balauced (differential mode) source/load!
Why use a balun? A balun is a circuit element intended to transform
differential mode (dipole) to common mode (coax). An RF choke consisting
of multiple turns of coax through an appropriate toroid or a number of
clamp-on ferrites on the coax at the feed point are appropriate, but not a
"balun" as such. The proposed "fixes" will choke common mode currents on
the external surface of the coax shield.
Dave - W?LEV
toggle quoted message
Show quoted text
On Wed, Nov 23, 2022 at 12:29 PM Barry K3EUI <k3euibarry@...> wrote: Just to check ¡ª¡ª
The resonant frequency of any dipole (center fed, OCF, or end-fed) is
determined only but the TOTAL length of the wire, and not be WHERE you feed
it.
(And maybe how high above ground or other nearby conductors).
Altering the feed point location only changes the input IMPEDANCE.
Center feds are typically 30-80 ohms (depending on height above ground).
OCF I¡¯ve seen at 200 to 600 ohms.
End-feds can be thousands of ohms.
Typically you see 1/3, 2/3 split (45 ft, 90 ft) for a 135 ft long wire,
which puts the impedance around 400 ohms.
I think some argue that for a 120-140 ft overall length, based on the
harmonics but you can try different locations depending on the BALUN ratio.
Barry k3eui
-- *Dave - W?LEV* *Just Let Darwin Work*
--
Dave - W?LEV
|
Um sich abzumelden, klicken Sie auf den Link unten in dieser E-Mail, wo es hei?t: Unsubscribe
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On 11/23/22 02:12, Peter, DG4EK wrote: Bitte nichts mehr Schicken
mein Mann ist Tod
Am 19. November 2022 15:19:17 MEZ schrieb N4RFC<Bob@...>:
Found the problem. From a post on github () I found that the settings for antialiasing had been depreciated.
By editing /usr/share/glib-2.0/schemas/org.gnome.settings-daemon.plugins.xsettings.gschema.xml and removing:
</schema>
<schema id="org.gnome.settings-daemon.plugins.xsettings.deprecated">
Then sudo glib-compile-schemas /usr/share/glib-2.0/schemas. This fixed the problem starting NanoVNA-Saver on Ubuntu 22.04.
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Re: Determining OCFD total length and split points
#circuit
On Tue, Nov 22, 2022 at 02:29 PM, Don - KM4UDX wrote:
How can we use the mighty nanoVNA to identify total length of a Off Center Fed
Dipole (OCFD)?
You MIGHT be able to do it with 2 measurements. Use the TDR function to measure one section (lelement) and then the other section. I assume that you would have to reverse the NanoVNA's connection to the co-ax (or other leadin) between measurements. Then compare the difference in lengths. If you have some spare wire and coax, it might be easiest to test the method with some wire and coax at ground level first. -- Doug, K8RFT
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Mein herzlichstes Beileid... Sie m¨¹ssen die emailgruppe verlassen damit da keine Mails mehr ankommen.
Dg9bfc sigi
Am 23.11.2022 11:12 schrieb "Peter, DG4EK" <info@...>:
toggle quoted message
Show quoted text
Bitte nichts mehr Schicken
mein Mann ist Tod
Am 19. November 2022 15:19:17 MEZ schrieb N4RFC <Bob@...>:
Found the problem.? From a post on github () I found that the settings
for antialiasing had been depreciated.
By editing
/usr/share/glib-2.0/schemas/org.gnome.settings-daemon.plugins.xsettings.gschema.xml
and removing:
? </schema>
? <schema id="org.gnome.settings-daemon.plugins.xsettings.deprecated">
Then sudo glib-compile-schemas /usr/share/glib-2.0/schemas.? This fixed
the problem starting NanoVNA-Saver on Ubuntu 22.04.
--
Diese Nachricht wurde von meinem Android-Ger?t mit K-9 Mail gesendet.
|
Re: Determining OCFD total length and split points
#circuit
... You have to feed ocf with a 1 to 4 and a good choke
Measure over a halfwave (or multiple of) cable (to see same resistance as on feedpoint).
Easy as baking cakes.
DJ0IP made several dozen ocfd versions and messured them (different lengths and split ratios).
And he 3xacrly explains that antenna.
Cwntre loaded ocfd adds a few more bands with low swr. So you also should think about that.
Dg9bfc sigi
Am 23.11.2022 15:07 schrieb Jim Lux <jimlux@...>:
toggle quoted message
Show quoted text
On 11/23/22 4:28 AM, Barry K3EUI wrote:
Just to check ¡ª¡ª
The resonant frequency of any dipole (center fed, OCF, or end-fed) is determined only but the TOTAL length of the wire, and not be WHERE you
feed it.
(And maybe how high above ground or other nearby conductors).
Altering the feed point location only changes the input IMPEDANCE.
Center feds are typically 30-80 ohms (depending on height above ground). OCF I¡¯ve seen at 200 to 600 ohms.
End-feds can be thousands of ohms.
Typically you see 1/3, 2/3 split (45 ft, 90 ft) for a 135 ft long wire, which puts the impedance around 400 ohms.
I think some argue that for a 120-140 ft overall length, based on the harmonics but you can try different locations depending on the BALUN
ratio.
Barry k3eui
Getting back to the original question - can you use the NanoVNA to
determine where the feed point is in an offcenter dipole:
NanoVNA can easily determine resonant frequency (where X=0).
Once you've got that, you'll know R at the resonance.
The question is whether there is a consistent relationship between R and
"split point"?? If R = 72, then you know it's in the middle of the
dipole.? But If there's droop in the dipole, that changes the R (e.g.
120 degrees gives you about 50 ohms; and diameter of the wires changes
the resistance as you move out.
So the short answer might be "maybe" -
You could build a model in NEC, and then iterate it until R matches what
you measured. Somewhere around, I have a plot of R vs split for a dipole
from a series of modeled scenarios. I'll look for it.
Or you could use 4nec2 or one of the other tools
|
Re: Determining OCFD total length and split points
#circuit
On 11/23/22 4:28 AM, Barry K3EUI wrote: Just to check ¡ª¡ª
The resonant frequency of any dipole (center fed, OCF, or end-fed) is determined only but the TOTAL length of the wire, and not be WHERE you feed it.
(And maybe how high above ground or other nearby conductors).
Altering the feed point location only changes the input IMPEDANCE.
Center feds are typically 30-80 ohms (depending on height above ground).
OCF I¡¯ve seen at 200 to 600 ohms.
End-feds can be thousands of ohms.
Typically you see 1/3, 2/3 split (45 ft, 90 ft) for a 135 ft long wire, which puts the impedance around 400 ohms.
I think some argue that for a 120-140 ft overall length, based on the harmonics but you can try different locations depending on the BALUN ratio.
Barry k3eui
Getting back to the original question - can you use the NanoVNA to determine where the feed point is in an offcenter dipole: NanoVNA can easily determine resonant frequency (where X=0). Once you've got that, you'll know R at the resonance. The question is whether there is a consistent relationship between R and "split point" If R = 72, then you know it's in the middle of the dipole. But If there's droop in the dipole, that changes the R (e.g. 120 degrees gives you about 50 ohms; and diameter of the wires changes the resistance as you move out. So the short answer might be "maybe" - You could build a model in NEC, and then iterate it until R matches what you measured. Somewhere around, I have a plot of R vs split for a dipole from a series of modeled scenarios. I'll look for it. Or you could use 4nec2 or one of the other tools
|
Re: Determining OCFD total length and split points
#circuit
Just to check ¡ª¡ª
The resonant frequency of any dipole (center fed, OCF, or end-fed) is determined only but the TOTAL length of the wire, and not be WHERE you feed it.
(And maybe how high above ground or other nearby conductors).
Altering the feed point location only changes the input IMPEDANCE.
Center feds are typically 30-80 ohms (depending on height above ground).
OCF I¡¯ve seen at 200 to 600 ohms.
End-feds can be thousands of ohms.
Typically you see 1/3, 2/3 split (45 ft, 90 ft) for a 135 ft long wire, which puts the impedance around 400 ohms.
I think some argue that for a 120-140 ft overall length, based on the harmonics but you can try different locations depending on the BALUN ratio.
Barry k3eui
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Bitte nichts mehr Schicken
mein Mann ist Tod
Am 19. November 2022 15:19:17 MEZ schrieb N4RFC <Bob@...>:
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Found the problem. From a post on github () I found that the settings for antialiasing had been depreciated.
By editing /usr/share/glib-2.0/schemas/org.gnome.settings-daemon.plugins.xsettings.gschema.xml and removing:
</schema>
<schema id="org.gnome.settings-daemon.plugins.xsettings.deprecated">
Then sudo glib-compile-schemas /usr/share/glib-2.0/schemas. This fixed the problem starting NanoVNA-Saver on Ubuntu 22.04.
--
Diese Nachricht wurde von meinem Android-Ger?t mit K-9 Mail gesendet.
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Re: Determining OCFD total length and split points
#circuit
this is a really good article on ocfd at various different places.
seems you can select from about 20% to over 33%.
All depends on your prefered frequencies.
There is no definative 'point' each of us has differing requirements.
My own is aout 1/3 - 2/3 ... but that is as much to fit it into the space(s) available.
Have fun...
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Re: Determining OCFD total length and split points
#circuit
OCFD puts the feedpoint at 5/8lambda from one end. That would be about 81-82ft for a 80m antenna.
Stephen W9SK
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Don - KM4UDX Sent: Tuesday, November 22, 2022 11:30 AM To: [email protected]Subject: [nanovna-users] Determining OCFD total length and split points #circuit Hello! How can we use the mighty nanoVNA to identify total length of a Off Center Fed Dipole (OCFD)? Or Normally a 80m dipole is about 130 feet the sides are 130/2. Can the nano measure the total length or the sides? An OCFD moves the split point from 50/50 to some other point. Can the NanoVNA determine or infer the split point? Thank you nanoVNA experts!
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Larry McElhiney
Mike C.
Barry K3EUI
Peter, DG4EK
Jon-G0MYW
Stephen W9SK