Date   
Re: OT: App that keeps track of "Or Best Offer" auctions on eBay to tell you what a seller will accept.

David Berlind
 

I think those one of a kind opportunities still exist on eBay. To one of
the points made by Dennis, once I know what I'm looking for across a
variety of marketplaces (eBay, CraigList, the Facebook Marketplace,
ShopGoodWill.com, etc.), the first thing I do is research what that item
has historically sold for on eBay. When you search eBay for an item, you
can filter the search to "Completed Items." (as opposed to active
listings). The results don't just included completed auctions, but also
Buy-It-Now listings that were optionally enabled with the "Make Offer"
button. For those listings, you will never know how much was actually paid
for the item. They only show the Buy-It-Now price. The actual sale price
could have been the Buy-It-Now price, or something less. But, of the
completed auctions where there was actual bidding, you can see what the
winning bids were, and that's what I go by to get some idea of the current
market value of something.

Then, I start to scour all the marketplaces for that item. Sometimes, I end
up buying on eBay. Other times not. The most recent example of this for me
was a B&K 875B LCR meter. My eBay research revealed that they were selling
for $125-$150. I watched all the marketplaces (easier to automate for some
than others). On eBay, I set up an alert to let me know when their were new
listings for that item. Then, as those listings come up, if it's an
auction, I put that actual listing on my eBay watch list (click the "watch"
button on the listing). As the auction gets closer to ending, eBay will
send you notifications that it's almost over. Yesterday, after getting a
notification and as the auction was minutes away from closing, .... I had
it open .. and got the item for $64 (shipping included)

https://www.ebay.com/itm/B-K-Model-875B-LCR-Meter-with-test-leads-and-manual/113745581598

I followed this same technique with the Tek signal standardizer plug in
that I just bought a couple of weeks ago off eBay for calibrating my 7000
series scopes (acquired for $77.. including shipping).

If there's insufficient historical data, and you're patient, another trick
is to wait for one to come up for auction, and just watch it all the way to
the end to see what it sells for a couple of times. I put this exact
technique to use today for a nearly new Atomos Ninja V external video
monitor that sold for $594 with shipping. Now I know what the most I should
pay is.

https://www.ebay.com/itm/Atomos-Ninja-V-5-4K-HDMI-Recording-Monitor-SSD-Battery-HDMI-Cable-Mint-/323812493375

For Craigslist, you can use Google Alerts to notify you when the item comes
up for sale anywhere in the country. Just use "craigslist.org" as the
target domain in the Google Alert search string.

OK, hope this helps.

On Wed, May 22, 2019 at 2:04 PM Dennis Tillman W7PF <@Dennis_Tillman_W7PF>
wrote:

There are certainly a lot of people asking me to let them know if I ever
find it again. I remember using all the strategies you describe when eBay
was a lot less controlling of their own auctions. Everything you can learn
about a seller, the price an item sells at, and other bidders behavior
rpatterns is knowledge you can use to improve your odds of winning an
auction. eBay has gradually caught on to this and has steadily placed
restrictions on every bit of information that can be used to give you an
edge.

You have seen the very same thing happening. I think I was very lucky to
have been so active on eBay so many years ago. At the time I never realized
that it wouldn't always be that way. This is unfortunate, but it explains
why I turn to eBay for different things now than I did before. Gone are the
exciting one of a kind items you can sometimes get for a ridiculous price
because your put in a bid early and the sniping site had a meltdown moments
before the auction ended and didn’t place any snipes. I remember a few
times when I won something for the opening bid price that way.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
tekscopegroup@...
Sent: Wednesday, May 22, 2019 10:04 AM
Subject: Re: [TekScopes] OT: App that keeps track of "Or Best Offer"
auctions on eBay to tell you what a seller will accept.

Back a few years before ebay started to obfuscate all the information on
bidders and sellers an app like that would still have been possible to work
on the public information that was available on any ebay member. Back then
I was even doing myself some manual background checks on other bidders I
was competing with for an item. I used to check on their previous bids
history what items they won/lost etc to try and find patterns, and also how
they liked to send in their highest bid (some people like to send even
amounts, others like weird patterns, like $12.34 or $111.11 and so on) to
try to anticipate their next maximum bid. Also back then if you managed to
get in your bid in the last 10-15 seconds before the end you usually won if
your bid was high enough, and I was quite successful (inc synchronizing the
PC clock with ebay clock, make sure to be freshly logged in, etc). I even
had friends asking me to snag something of ebay for them. But nowadays they
even automated sniping and sometimes you get beaten by a bid sent 1-2
seconds before the auction ends. Anyway gathering relevant information on
other bidders or sellers is now for the most part no longer possible as it
used to be. So unless this app has a way to sneak into ebay's servers and
bypass whatever security they have in place to protect their databases I
don't see how an app like that is still possible. Unless someone found a
backdoor.




--
Dennis Tillman W7PF
TekScopes Moderator



Re: OT: App that keeps track of "Or Best Offer" auctions on eBay to tell you what a seller will accept.

Tom Gardner
 

On 22/05/19 19:55, David Berlind wrote:
The results don't just included completed auctions, but also
Buy-It-Now listings that were optionally enabled with the "Make Offer"
button. For those listings, you will never know how much was actually paid
for the item. They only show the Buy-It-Now price. The actual sale price
could have been the Buy-It-Now price, or something less.
Goto watchcount.com and paste the ebay item number into the keywords box.

For example:
https://www.ebay.co.uk/itm/Datron-1061A-multimeter-6-5-digit-DC-volts-AC-volts-Resistance-current-GPIB/113707651429

Therefore item number 113707651429

shows


Seller:
testelectro <http://www.watchcount.com/go/?seller=testelectro&cid=ilu->[efb <http://www.watchcount.com/go/?cid=ilu-efb-&url=https%3A%2F%2Ffeedback.ebay.co.uk%2Fws%2FeBayISAPI.dll%3FViewFeedback2%26ftab%3DFeedbackAsSeller%26userid%3Dtestelectro>][sld <http://www.watchcount.com/completed.php?bfw=1&bslr=testelectro#serp>]


View Count:
 104
 Watch Count:
3 <http://www.watchcount.com/go/?item=113707651429&cid=ilu->
Start Time:
 Thursday, 04-Apr-19 08:11:44UTC
End Time:
 Friday, 12-Apr-19 13:30:01UTC (40.28 days ago)
Current Bid/Price (GBP):
£ 295.00
Best Offer Enabled
Sold For (GBP):
 £ 270.00(check price here? –>) [History <http://www.watchcount.com/go/?cid=ilu-ihist-113707651429-&url=https%3A%2F%2Foffer.ebay.co.uk%2Fws%2FeBayISAPI.dll%3FViewBidsLogin%26item%3D113707651429>]

Further of my Tek 2465A S/N B019121

Lawrence Joy
 

To Brad, AA1IP,
I did not use your aluminum foil over the tip of my Torx T-10 suggestion. I asked on my local 2 m net and it was suggested to use an Allen (hex key) wrench. I used a 7/64" size Allen wrench, and a pair of pliers, and was able to get that last screw out. I checked one of the "good" screws and the 7/64" size would not fit, so that particular bad boy screw was deformed.

To everyone,
Now that I have the A2A1--Regulator CCA and the A3--Inverter CCA separated I need to do one more removal. How do you get the black plastic cover off the black plastic bottom that contains the A3C1021 and A3C1022, 290 µF 200 V DC capacitors? The parts layout drawing of the A3 CCA of Figure 10-13 does not show this. The top is loose and I tried a flat blade screwdriver around the sides I could get to but I didn't want to break anything, or is that what I have to do?
Tnx, WN8P, Larry

Re: Further of my Tek 2465A S/N B019121

tom jobe
 

Look at the center of the black plastic cover, there is plastic prong made right in the cover that sticks straight down with a little barb on the end of it.
You push the prong to the side just a little and the cover comes off.
Those two large capacitors are rarely a problem, and most folks would have you leave them alone if the ESR checks out okay.
tom jobe...

On 5/22/2019 2:45 PM, Lawrence Joy via Groups.Io wrote:
To Brad, AA1IP,
I did not use your aluminum foil over the tip of my Torx T-10 suggestion. I asked on my local 2 m net and it was suggested to use an Allen (hex key) wrench. I used a 7/64" size Allen wrench, and a pair of pliers, and was able to get that last screw out. I checked one of the "good" screws and the 7/64" size would not fit, so that particular bad boy screw was deformed.

To everyone,
Now that I have the A2A1--Regulator CCA and the A3--Inverter CCA separated I need to do one more removal. How do you get the black plastic cover off the black plastic bottom that contains the A3C1021 and A3C1022, 290 µF 200 V DC capacitors? The parts layout drawing of the A3 CCA of Figure 10-13 does not show this. The top is loose and I tried a flat blade screwdriver around the sides I could get to but I didn't want to break anything, or is that what I have to do?
Tnx, WN8P, Larry

Re: OT: App that keeps track of "Or Best Offer" auctions on eBay to tell you what a seller will accept.

 

Hi Tom,
While I was searching for the app I tried to describe in my original post I did find WatchCount.com site. I also found the GoofBid site (www.goofbid.com).
MORE IMPORTANTLY I found out where I got the original information from: IT WAS YOU:)

This is the link to the original mail about WatchCount that you sent:
https://groups.io/g/TekScopes/message/148676

I haven't quite figured out what I am doing wrong with GoofBid's eBay Best Offers Tool and eBay Best Offer History Tool or where I first found out about it. It is what I was looking for where you can enter a user's eBay ID into it and it will show you all the times they accepted an offer. At least that is what I think it does. So far I haven't gotten to give me any results at all when I enter a seller name who I know has things they will accept an offer on.

I think they have changed the user interface so I didn't recognize it until just now even though Petru Ulici pointed it out to me yesterday

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Tom Gardner
Sent: Wednesday, May 22, 2019 1:20 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] OT: App that keeps track of "Or Best Offer" auctions on eBay to tell you what a seller will accept.

On 22/05/19 19:55, David Berlind wrote:
The results don't just included completed auctions, but also
Buy-It-Now listings that were optionally enabled with the "Make Offer"
button. For those listings, you will never know how much was actually
paid for the item. They only show the Buy-It-Now price. The actual
sale price could have been the Buy-It-Now price, or something less.
Goto watchcount.com and paste the ebay item number into the keywords box.

For example:
https://www.ebay.co.uk/itm/Datron-1061A-multimeter-6-5-digit-DC-volts-AC-volts-Resistance-current-GPIB/113707651429

Therefore item number 113707651429

shows
Seller:
testelectro <http://www.watchcount.com/go/?seller=testelectro&cid=ilu->[efb
<http://www.watchcount.com/go/?cid=ilu-efb-&url=https%3A%2F%2Ffeedback.ebay.co.uk%2Fws%2FeBayISAPI.dll%3FViewFeedback2%26ftab%3DFeedbackAsSeller%26userid%3Dtestelectro>][sld
<http://www.watchcount.com/completed.php?bfw=1&bslr=testelectro#serp>]


View Count:
104
Watch Count:
3 <http://www.watchcount.com/go/?item=113707651429&cid=ilu->
Start Time:
Thursday, 04-Apr-19 08:11:44UTC
End Time:
Friday, 12-Apr-19 13:30:01UTC (40.28 days ago)
Current Bid/Price (GBP):
£ 295.00
Best Offer Enabled
Sold For (GBP):
£ 270.00(check price here? –>) [History
<http://www.watchcount.com/go/?cid=ilu-ihist-113707651429-&url=https%3A%2F%2Foffer.ebay.co.uk%2Fws%2FeBayISAPI.dll%3FViewBidsLogin%26item%3D113707651429>]
--
Dennis Tillman W7PF
TekScopes Moderator

Re: OT: App that keeps track of "Or Best Offer" auctions on eBay to tell you what a seller will accept.

Tom Gardner
 

Regrettably goofbid appears to return zero results, at the moment.

Maybe ebay have stymied them, maybe they have a simple server problem. I hope it is the latter.

On 22/05/19 23:12, Dennis Tillman W7PF wrote:
Hi Tom,
While I was searching for the app I tried to describe in my original post I did find WatchCount.com site. I also found the GoofBid site (www.goofbid.com).
MORE IMPORTANTLY I found out where I got the original information from: IT WAS YOU:)

This is the link to the original mail about WatchCount that you sent:
https://groups.io/g/TekScopes/message/148676

I haven't quite figured out what I am doing wrong with GoofBid's eBay Best Offers Tool and eBay Best Offer History Tool or where I first found out about it. It is what I was looking for where you can enter a user's eBay ID into it and it will show you all the times they accepted an offer. At least that is what I think it does. So far I haven't gotten to give me any results at all when I enter a seller name who I know has things they will accept an offer on.

I think they have changed the user interface so I didn't recognize it until just now even though Petru Ulici pointed it out to me yesterday

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Tom Gardner
Sent: Wednesday, May 22, 2019 1:20 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] OT: App that keeps track of "Or Best Offer" auctions on eBay to tell you what a seller will accept.

On 22/05/19 19:55, David Berlind wrote:
The results don't just included completed auctions, but also
Buy-It-Now listings that were optionally enabled with the "Make Offer"
button. For those listings, you will never know how much was actually
paid for the item. They only show the Buy-It-Now price. The actual
sale price could have been the Buy-It-Now price, or something less.
Goto watchcount.com and paste the ebay item number into the keywords box.

For example:
https://www.ebay.co.uk/itm/Datron-1061A-multimeter-6-5-digit-DC-volts-AC-volts-Resistance-current-GPIB/113707651429

Therefore item number 113707651429

shows
Seller:
testelectro <http://www.watchcount.com/go/?seller=testelectro&cid=ilu->[efb
<http://www.watchcount.com/go/?cid=ilu-efb-&url=https%3A%2F%2Ffeedback.ebay.co.uk%2Fws%2FeBayISAPI.dll%3FViewFeedback2%26ftab%3DFeedbackAsSeller%26userid%3Dtestelectro>][sld
<http://www.watchcount.com/completed.php?bfw=1&bslr=testelectro#serp>]


View Count:
104
Watch Count:
3 <http://www.watchcount.com/go/?item=113707651429&cid=ilu->
Start Time:
Thursday, 04-Apr-19 08:11:44UTC
End Time:
Friday, 12-Apr-19 13:30:01UTC (40.28 days ago)
Current Bid/Price (GBP):
£ 295.00
Best Offer Enabled
Sold For (GBP):
£ 270.00(check price here? –>) [History
<http://www.watchcount.com/go/?cid=ilu-ihist-113707651429-&url=https%3A%2F%2Foffer.ebay.co.uk%2Fws%2FeBayISAPI.dll%3FViewBidsLogin%26item%3D113707651429>]



7904 excessive shadow/flare

unclebanjoman
 

Hi,
I've just repaired a 7904. Usual problem, SMPS not working.
Then I've checked all voltages, HV voltages, etc.. all it's fine, very good.
Just some adjustments to Z board, focus and so on.
The scope is in very good conditions, the trace is well defined, bright and sharp.

But there is an annoying problem that I don't think is normal.

It is the usual shadow / halo / flare effect but while in my two 7854s and 465s that already own this effect only manifests itself with somewhat high brightness, in this particular 7904 with low/normal brightness the halo/flare effect it is already visible and definitely annoying.
To give an idea I took a picture that you can see at

https://groups.io/g/TekScopes/album?id=90746

I reiterate that the photo was taken with the intensity controls were set for a normal brightness even if in the photo it seems that the brightness is too high.

I've compared side-by-side my 7904 with my 7854 (they should use the same tube model) :while the 7854 the flare/halo effect is unnoticeable, the 7904 is definitely visible already with moderate brightness.

I'm puzzled.
Could it be the crt damaged by some mechanical shock?
What do you think about it?

Thanks,
Max

Re: OT: App that keeps track of "Or Best Offer" auctions on eBay to tell you what a seller will accept.

David Berlind
 

Goofbid and other sites/apps that integrate with eBay probably work through eBay's API which has lost functionality (ie: certain fields of data) over the years due to privacy concerns, security issues, GDPR, etc. These changes irreparably break the applications that rely on them in the ways that you are noticing. The same has happened to many other APIs from popular sites.

On May 22, 2019 6:29:04 PM "Tom Gardner" <tggzzz@...> wrote:

Regrettably goofbid appears to return zero results, at the moment.

Maybe ebay have stymied them, maybe they have a simple server problem. I hope it
is the latter.


On 22/05/19 23:12, Dennis Tillman W7PF wrote:
Hi Tom,
While I was searching for the app I tried to describe in my original post I did find WatchCount.com site. I also found the GoofBid site (www.goofbid.com).
MORE IMPORTANTLY I found out where I got the original information from: IT WAS YOU:)

This is the link to the original mail about WatchCount that you sent:
https://groups.io/g/TekScopes/message/148676

I haven't quite figured out what I am doing wrong with GoofBid's eBay Best Offers Tool and eBay Best Offer History Tool or where I first found out about it. It is what I was looking for where you can enter a user's eBay ID into it and it will show you all the times they accepted an offer. At least that is what I think it does. So far I haven't gotten to give me any results at all when I enter a seller name who I know has things they will accept an offer on.

I think they have changed the user interface so I didn't recognize it until just now even though Petru Ulici pointed it out to me yesterday

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Tom Gardner
Sent: Wednesday, May 22, 2019 1:20 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] OT: App that keeps track of "Or Best Offer" auctions on eBay to tell you what a seller will accept.

On 22/05/19 19:55, David Berlind wrote:
The results don't just included completed auctions, but also
Buy-It-Now listings that were optionally enabled with the "Make Offer"
button. For those listings, you will never know how much was actually
paid for the item. They only show the Buy-It-Now price. The actual
sale price could have been the Buy-It-Now price, or something less.
Goto watchcount.com and paste the ebay item number into the keywords box.

For example:
https://www.ebay.co.uk/itm/Datron-1061A-multimeter-6-5-digit-DC-volts-AC-volts-Resistance-current-GPIB/113707651429

Therefore item number 113707651429

shows
Seller:
testelectro <http://www.watchcount.com/go/?seller=testelectro&cid=ilu->[efb
<http://www.watchcount.com/go/?cid=ilu-efb-&url=https%3A%2F%2Ffeedback.ebay.co.uk%2Fws%2FeBayISAPI.dll%3FViewFeedback2%26ftab%3DFeedbackAsSeller%26userid%3Dtestelectro>][sld
<http://www.watchcount.com/completed.php?bfw=1&bslr=testelectro#serp>]


View Count:
104
Watch Count:
3 <http://www.watchcount.com/go/?item=113707651429&cid=ilu->
Start Time:
Thursday, 04-Apr-19 08:11:44UTC
End Time:
Friday, 12-Apr-19 13:30:01UTC (40.28 days ago)
Current Bid/Price (GBP):
£ 295.00
Best Offer Enabled
Sold For (GBP):
£ 270.00(check price here? –>) [History
<http://www.watchcount.com/go/?cid=ilu-ihist-113707651429-&url=https%3A%2F%2Foffer.ebay.co.uk%2Fws%2FeBayISAPI.dll%3FViewBidsLogin%26item%3D113707651429>]




Procedure to measure rf watts

Randy.AB9GO
 

Hello everyone,

I have a need to check the calibration on some low power watt meters (10 watts or less, 21 megahertz or less) and was wondering if anybody had a favorite procedure using their scope to measure peak-to-peak rf voltage without letting out the magic smoke. My thought is to use a t connector, hook one side to the transmitter, one side to a dummy load and then the center connector straight to the 10X oscilloscope probe. Any other precautions I should take?

Thank you,
Randy.

Re: Photo Storage Space Solution, was IMPORTANT: Photos are eating up our storage

nonIonizing EMF
 

I was wondering if moving the images and details related like including the link to the groups.io or other post to Tekwiki might be a solution. I'm not sure about the server limitations and expense there however.

Re: 7904 excessive shadow/flare

radioconnection@...
 

Looks like an out of phase ghost image? Signal reflection due to SWR on the probe cable?

Try another signal source and different cable.

Pete

Re: Photo Storage Space Solution, was IMPORTANT: Photos are eating up our storage

Harvey White
 

Didn't tekscopes have some other groups that were created solely for image storage back on Yahoo?

Harvey

On 5/22/2019 7:02 PM, nonIonizing EMF wrote:
I was wondering if moving the images and details related like including the link to the groups.io or other post to Tekwiki might be a solution. I'm not sure about the server limitations and expense there however.




Re: 7904 excessive shadow/flare

unclebanjoman
 

No, the artifact is visible with any type of signal.
It also appears using the signal standardizer. I used the latter today to perform some calibrations on my 7904 and I was very irritated by this halo / flare effect.
With sweep rates of 0.1-0.5 sec and no signal applied is clearly visible the usual "globus" leading/lagging the spot.
Already with moderate brightness the artifact is visible.

Max

Re: Old Tektronix Books

Dave Wise
 

Guilty. Oops. I guess I skipped words and saw what I wished were true.

I know I've read Typical Oscilloscope Circuitry. The physical book, in my hands. But I'm pretty sure I don't own a copy. It's a mystery.
Worldcat.org indicates several libraries with copies, including, for you in northwest Oregon, Pacific University in Forest Grove. You can probably get it via inter-library loan.

Dave Wise

PS: My rotten memory believes that the schematics were 535 and 545.
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of ROLYNN PRECHTL K7DFW <k7dfw@...>
Sent: Wednesday, May 22, 2019 11:10 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Old Tektronix Books

The "Typical Oscilloscope Circuitry" book. Rolynn said it was at w140 ("TekWiki"), but I couldn't find it so I asked him where it was in the w140 site.

===========================================================================================

Not even close.

Rolynn said that the:

1961 publication eliminates some.
(1961 publication date eliminates some of the scopes from where the schematics came from)

The power supply might be a 531/535/541 but I'm not going to spend any time with this since the manuals are on TekWiki.

(the manuals for the potential scope candidates are on TekWiki and to do your own detective work to find out which instrument schematics are in the book)

Clear as a bell - to me.

Rolynn

Re: Procedure to measure rf watts

Bob Albert
 

I use my venerable HP410B.  The ac probe has wide bandwidth and the most sensitive range of 1 V should suffice for all but the weakest power from a transmitter.  Full scale corresponds to 20 mW.  Half scale, or 0.5 Volt, 5 mW.
Sure you can use an oscilloscope.  You will have some calculation to do.  Further, you would be able to ascertain whether you are working with something close to a sine wave.
Ideally, use both instruments, one for checking waveform and the other for a quantitative reading.  The load, of course, needs to be purely resistive.  If not, your 'power' reading will be wrong.
In any case, an oscilloscope isn't the best tool for precise measurements.  The trace width and screen nonlinearities need to be considered.  A spectrum analyzer might be a good idea, since it would show each frequency component and allow one to decide if any are large enough to influence the result.  Most spectrum analyzers have 50 or 75 Ohm input already in place; the pitfall there is to make sure you don't burn out the termination.  Ten Watts is too much, and most aren't safe above 1 Watt or less.  A dummy load and attenuator might be a good idea.
When I measure the power out of my ham transmitter I can get an accurate reading with the HP voltmeter.  I use either a dummy load or an antenna with close to 1:1 SWR.  Without the linear amplifier I get around 65-70 V reading (100 W or so) and with the amplifier about 220-250 Volts (over 1 kW), depending on tuning and load quality.  The HP pointer movement is so well damped that I can get peak readings when operating pulsed, such as a series of CW dots.
I also have an oscilloscope to see the wave; I couple it to the system with a loop pickup.  I connect a coaxial cable to the 'scope and short the other end around one of my voltmeter leads.  Thus, inductive pickup.
When I use audio modulation I can measure peak envelope power on the voltmeter.  The 'scope will enable me to adjust the modulation such that I don't get clipping.  I can also verify the performance of the speech processor.
Bob

On Wednesday, May 22, 2019, 4:01:03 PM PDT, Randy.AB9GO <@AB9GO> wrote:

Hello everyone,

I have a need to check the calibration on some low power watt meters (10 watts or less, 21 megahertz or less) and was wondering if anybody had a favorite procedure using their scope to measure peak-to-peak rf voltage without letting out the magic smoke.  My thought is to use a t connector, hook one side to the transmitter, one side to a dummy load and then the center connector straight to the 10X oscilloscope probe. Any other precautions I should take?

Thank you,
Randy.

Re: Procedure to measure rf watts

@0culus
 

On Wed, May 22, 2019 at 04:00 PM, Randy.AB9GO wrote:


Hello everyone,

I have a need to check the calibration on some low power watt meters (10 watts
or less, 21 megahertz or less) and was wondering if anybody had a favorite
procedure using their scope to measure peak-to-peak rf voltage without letting
out the magic smoke. My thought is to use a t connector, hook one side to the
transmitter, one side to a dummy load and then the center connector straight
to the 10X oscilloscope probe. Any other precautions I should take?

Thank you,
Randy.
I will say above anything else, 10W is way too much power to be putting into most test equipment, especially spectrum analyzers. You *will* burn up something in the frontend and then you'll be sad. You want something like an RF sampling tee that will couple a much smaller version of your TX signal into your instrument.

Sean

Re: Procedure to measure rf watts

Richard Knoppow
 

At communication frequencies I use a General Radio 1800A mainly because I have the proper adapter for the probe. The 410B is fine but its adapters for any of the more common coaxial connectors are pretty scarce. Otherwise its fine. The 1800A takes a shell for a GR 874 connector which screws into the end of the probe, the banana plug acting as the center conductor. I then use an N type T with UHF adaptors on two ends and the probe in the center. I have a couple of dummy loads which have been measured on a GR RF bridge so I know their actual impedance at the measurement frequency. In general a DC resistance measurement comes close and they are pretty non-reactive. I can then calculate the power with reasonable accuracy.
Both the 1800A and 410B have single diode rectifiers for RF and both have the usual characteristic of being square law at small voltages transitioning to peak reading at high voltages. The scales are calibrated in the RMS value of a sine wave and both have different scales for low and high voltages as required by the characteristic of the diode. I have calibrated my MFJ tuner/SWR meter/power meter using this arrangement. It seems to be reasonably accurate. A scope could be used but as you say requires some calculation because it reads peak-to-peak.
Nothing is as simple as it seems or as you would prefer.
OTOH, a scope can tell you an awful lot about what is going on in the transmitter.

On 5/22/2019 5:39 PM, Bob Albert via Groups.Io wrote:
I use my venerable HP410B.  The ac probe has wide bandwidth and the most sensitive range of 1 V should suffice for all but the weakest power from a transmitter.  Full scale corresponds to 20 mW.  Half scale, or 0.5 Volt, 5 mW.
Sure you can use an oscilloscope.  You will have some calculation to do.  Further, you would be able to ascertain whether you are working with something close to a sine wave.
Ideally, use both instruments, one for checking waveform and the other for a quantitative reading.  The load, of course, needs to be purely resistive.  If not, your 'power' reading will be wrong.
In any case, an oscilloscope isn't the best tool for precise measurements.  The trace width and screen nonlinearities need to be considered.  A spectrum analyzer might be a good idea, since it would show each frequency component and allow one to decide if any are large enough to influence the result.  Most spectrum analyzers have 50 or 75 Ohm input already in place; the pitfall there is to make sure you don't burn out the termination.  Ten Watts is too much, and most aren't safe above 1 Watt or less.  A dummy load and attenuator might be a good idea.
When I measure the power out of my ham transmitter I can get an accurate reading with the HP voltmeter.  I use either a dummy load or an antenna with close to 1:1 SWR.  Without the linear amplifier I get around 65-70 V reading (100 W or so) and with the amplifier about 220-250 Volts (over 1 kW), depending on tuning and load quality.  The HP pointer movement is so well damped that I can get peak readings when operating pulsed, such as a series of CW dots.
I also have an oscilloscope to see the wave; I couple it to the system with a loop pickup.  I connect a coaxial cable to the 'scope and short the other end around one of my voltmeter leads.  Thus, inductive pickup.
When I use audio modulation I can measure peak envelope power on the voltmeter.  The 'scope will enable me to adjust the modulation such that I don't get clipping.  I can also verify the performance of the speech processor.
Bob
On Wednesday, May 22, 2019, 4:01:03 PM PDT, Randy.AB9GO <@AB9GO> wrote:
Hello everyone,
I have a need to check the calibration on some low power watt meters (10 watts or less, 21 megahertz or less) and was wondering if anybody had a favorite procedure using their scope to measure peak-to-peak rf voltage without letting out the magic smoke.  My thought is to use a t connector, hook one side to the transmitter, one side to a dummy load and then the center connector straight to the 10X oscilloscope probe. Any other precautions I should take?
Thank you,
Randy.
--
Richard Knoppow
dickburk@...
WB6KBL

Re: Procedure to measure rf watts

Jim Ford
 

Definitely use a directional coupler or an attenuator.I assume that the flow-through wattmeters like those made by Bird have couplers inside those plug-in modules.Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: sdturne@q.com Date: 5/22/19 6:25 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Procedure to measure rf watts On Wed, May 22, 2019 at 04:00 PM, Randy.AB9GO wrote:>> Hello everyone,> > I have a need to check the calibration on some low power watt meters (10 watts> or less, 21 megahertz or less) and was wondering if anybody had a favorite> procedure using their scope to measure peak-to-peak rf voltage without letting> out the magic smoke. My thought is to use a t connector, hook one side to the> transmitter, one side to a dummy load and then the center connector straight> to the 10X oscilloscope probe. Any other precautions I should take?> > Thank you,> Randy.>I will say above anything else, 10W is way too much power to be putting into most test equipment, especially spectrum analyzers. You *will* burn up something in the frontend and then you'll be sad. You want something like an RF sampling tee that will couple a much smaller version of your TX signal into your instrument.Sean

Re: Latest firmware for TDS210 and TDS2CM?

Jared Cabot
 

I might actually have the newer version of the hardware.

My scope firmware is v2.03 and my module (It's actually a TDS2MM, not TDS2CM as I previously wrote) is v1.04
Are there any later versions than these? And is there any info on that programming fixture? I assume it would be almost unobtanium....

497p front panel cal failure (CF and Ref Lvl)

radioconnection@...
 

The first test in the manual for the center frequency and reference level self calibration fails. Otherwise, the instrument seems to be working normally. I can't find a detailed trouble shooting chart for that error.

Any suggestions where to start?

Pete