On 11/24/22 9:29 AM, Ho-Ro wrote: On Thu, Nov 24, 2022 at 05:47 PM, Paul M3VUV wrote:
measured the resistance on the s11 port on my vna ... it read 49 ohms ... is that normal ... ? On a NanoVNA the CHO port connects to a bridge with ~50 ohm DC resistance. See the schematic of at least one version. CH1 connects to a attenuator, also with approximately 50 ohm DC resistance. All RF devices have input and output resistance of 50 ¦¸ - unless you're in the TV business (they have 75 ¦¸) - otherwise youi'll get reflections (bad SWR).
That's not generally true - A lot of devices will have a RF impedance of 50 ohm resistive, but that's also only if the power is on and if the other ports are terminated in their expected impedances. And at the design frequency. For example, a Bias T might show infinite DC resistance, because there's a blocking capacitor. a typical power divider will NOT show 50 ohms DC resistance, depending on the configuration. A Wilkinson, certainly not, since it depends on the impedance transformation of the 1/4 wavelength lines. Same with a Lange coupler. A "triangle" resistive power divider might show 50 ohms DC, if the output ports are terminated in 50 ohms. One does want to be careful measuring the ports of RF devices with a ohmmeter, too. For instance the NanoVNA2 has some RF switches connected directly to the ports, and depending on the voltage of your ohmmeter, those could be damaged.
|
On Thu, Nov 24, 2022 at 05:47 PM, Paul M3VUV wrote: measured the resistance on the s11 port on my vna ... it read 49 ohms ... is that normal ... ? All RF devices have input and output resistance of 50 ¦¸ - unless you're in the TV business (they have 75 ¦¸) - otherwise youi'll get reflections (bad SWR). Martin
|
Re: max save slots on the vna "h" version running hugens fw
On Thu, Nov 24, 2022 at 04:45 PM, Paul M3VUV wrote:
Hi ,i have loaded this but cant seem to get swr to show on trace 1,it says
logmag,it used to have swr in yellow numerals in the top middle of the screen
with my old fw,any ideas?.
Paul, Trace 1? Yellow is the color of the 1st trace (Trace 0) - but nevertheless: Menu - Display - Trace - set Trace 0 active - Back - Format S11 (Refl) - set SWR active Enable/disable the other traces accordingly. Martin
|
Hi all,long story my homebrew pi network atu wasnt tuning so stuck my v2 vna on it to have a look,at one point in the c2(variable cap nearest the output jack for the rig)looked as iff the vanes were shorting to ground,after removing the said cap it actualy looked ok but both sides looked like shorting to ground,the cap was still wired to the atu at this point, also the vna was conected to the atu,my meter was belling out between both legs of the cap and ground,i disconnected the vna and it stopped buzzing,i then measured the resistance on the s11 port on my vna,ie the center pin and outer of the s11 plug,it read 49 ohms low enough to make my fluke 87 dmm buzz on resistance mode,is that normal or a diode sc in my vna front end?.
|
Re: max save slots on the vna "h" version running hugens fw
Hi ,i have loaded this but cant seem to get swr to show on trace 1,it says logmag,it used to have swr in yellow numerals in the top middle of the screen with my old fw,any ideas?.
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On 11/24/22 5:57 AM, N3MEL - Glenn wrote: Is there a document that better explains what the returned data from a sweep really means?
In terms of the raw message from the NanoVNA (in response to the "data" command)? It's real and imaginary of the reflection coefficient(for CH0) or transmission coefficient (for CH1) You'll also need to do a "sweep" command which returns the start and stop frequency, and number of points. The document I use is a pdf from 2019 called NanoVNA_Console_Commands_Dec 9-19.pdf It's on the wiki here /g/nanovna-users/wiki#For-Beginners-and-Experienced-Users73 de Glenn N3MEL
(FRNPA) 1st Responders Network of Pa
PKT:145.090 &?VARA HF:3.596?WL2K:145.670
Emergency Coordinator
Chester County ARES/RACES
|
Is there a document that better explains what the returned data from a sweep really means?
73 de Glenn N3MEL
(FRNPA) 1st Responders Network of Pa
PKT:145.090 &?VARA HF:3.596?WL2K:145.670
Emergency Coordinator
Chester County ARES/RACES
|
Re: Problem with eBay seller SV4401A: CAUTION11
#buying
I would also encourage you to try PayPal, and to include any independent statements you can get about the non-delivery of your item.
I raised a case with eBay about non-delivery of an item from a UK seller which may, in fact, have never been sent. eBay were unhelpful and did the same thing to me as they did to you: removed the item from my "purchased" list as soon as the case was opened. Fortunately I had email copies of all the invoices, shipping advice, etc. I submitted these to PayPal, and received a commitment to resolve the case one way or the other within a couple of weeks. Within an hour or two of submitting the case to PayPal, eBay closed the case - despite their tardiness in getting an actual human to discuss my case (never did achieve that). A few days later PayPal refunded my money, including shipping, taxes and foreign exchange charges. Although the amount involved was not huge, I considered the PayPal purchasing charges to be well worthwhile.
Don't waste your time with eBay, but do see if you can get some independent statement about the fictitious package for PayPal. And, as others have said, stay with the more reputable sellers - I only buy from "RF" oriented sellers (check out their "other items") with manufacturers' recommendations.
Regards, Peter.
|
Re: Problem with eBay seller SV4401A: CAUTION11
#buying
I'm careful, but my experience with PayPal fixing bad deals, frauds,
non-deliveries, etc, is very good and has been for years. I never leave
money with them.
Chuck
toggle quoted message
Show quoted text
On Wed, Nov 23, 2022 at 8:58 PM Mike C. <mg@...> wrote: 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
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
--
Chuck Cole ?K4TZO
|
Re: Problem with eBay seller SV4401A: CAUTION11
#buying
I've been lucky that I have not actually lost any money. I've always managed to get a refund. My close calls have all been on deals that seemed too good to be true. One was half the price of any other vendor with "free delivery" by FedEx!
Lesson (re)learned. If its too good to be true it probably isn't real, especially on the Internet.
toggle quoted message
Show quoted text
On Wed, Nov 23, 2022 at 02:37 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
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¡
|
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
toggle quoted message
Show quoted text
-----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
|
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
toggle quoted message
Show quoted text
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
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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
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Ho-Ro
Peter Hall, VK6HP/VK6MJM
Chuck Cole
Larry McElhiney
Mike C.
