Most likely Chinese Gov't is filtering a lot of info passing through the 'Great Firewall of China' due to COVID19 concerns and this is 'collateral damage'.
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On Thursday, March 5, 2020, 9:56:43 a.m. GMT-5, Salil Tembe <salil2106@...> wrote:
Larry,
The seller in Shenzhen is able to see it listed but I can't view it here in India.
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Salil Tembe
(Nuclearrambo.com)
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Larry,
The seller in Shenzhen is able to see it listed but I can't view it here in India.
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Salil Tembe
(Nuclearrambo.com)
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Did you actually find it listed on Taobao or are you attempting to buy through a seller that sold the older versions?
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On Thursday, March 5, 2020, 9:20:47 a.m. GMT-5, Salil Tembe <salil2106@...> wrote:
I reviewed the first version. I can test this one too. I'm trying to get it through my component dealer in Shenzhen. He is trying to get two for me.
Unfortunately, the taobao seller isnt responding to the messages he has sent.
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Salil Tembe
(Nuclearrambo.com)
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I reviewed the first version. I can test this one too. I'm trying to get it through my component dealer in Shenzhen. He is trying to get two for me.
Unfortunately, the taobao seller isnt responding to the messages he has sent.
--
Salil Tembe
(Nuclearrambo.com)
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same here? cannot find it anywhere
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On 05/03/2020 04:13, Gabriel Tenma White wrote: I've gotten news that it's started selling on taobao and tindie will soon follow; should show up if you search "nanovna v2" on taobao.
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I'm not a tech leader by any stretch but I do have a variety of radar antennas and waveguides for various freqs up to the device's 4.4GHz range that I'll use to test this on. So far, I haven't found it at Taobao or anywhere else.
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John AE5X
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Who is our group tech leader who is going to test it and give a report?
73
Glen K4KV
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On 3/4/2020 23:13, Gabriel Tenma White wrote: I've gotten news that it's started selling on taobao and tindie will soon follow; should show up if you search "nanovna v2" on taobao.
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Re: Ceramic filter measurement
@Bob,
Exactly. Be aware that the curves in the muRata datasheet does only show pass band vs real load. Imaginary loads like parasitic capacitance will also impact.
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Re: Anyone had news from Maggie King?
Chris - I didn't pay for DHL shipping. Apologies for being unclear.
vy 73, Russ
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Re: Anyone had news from Maggie King?
On Tue, Mar 3, 2020 at 01:09 PM, Russ@va3rr wrote:
My H4 arrived today. Although I didn't pay for it,
Russ, how does one (say, somebody like me!) get the option of not paying for one to get one?? ;-) -- Regards, Chris
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Re: Ceramic filter measurement
David Platt,
First the input has a L-network coil plus input C of the Jfet.
So the input impedance is likely under 2000 ohms maybe 75 ohms.
The gray areas on the drawing modules are triple tuned band
pass circuits, a real pain to dial them in but better than commonly
used transformers (only double or single tuned) of the day.
You will need a output pad as that likely has gain in excess of
18-40DB to protect the VNA input. Also a attenuator at the input
as over driving it will cause errors. Marantz did a lot of neat and
odd things over the years.
The 10.7 ceramic filters (not the narrower crystal filters) are typically
300 or 1500 ohm load.
Ceramic filter do not like DC applied to them ( lifespan issue).
The usual way to jig them is two back to back broad band transformers
to go from 50 to user defined impedance and the exact same back to
50 ohms. Hooked up on a board the networks can be "calibrated" for
loss and band width.
The filters are inserted and tested. Generally they are much wider than
the desired FM bandwidth so the critical item is center frequency.
Allison
----------------
No direct email, it goes to bit bucket due address harvesting in groups.IO
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Re: Ceramic filter measurement
Here's a few graphics from the Murata Ceramic filter manual. The first one shows the change in response, both amplitude and group delay, versus impedance load. The next one is Murata's suggested filter test setup.
Bob
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Re: Ceramic filter measurement
Right.
Small comment: Be careful on layout around the in/out pins on the filter. I can see on your picture you might have quite some capacitance from in/out pins to ground.
Normally ground is keept away also on inner layers.
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Re: SO-239 standards for HF Band-pass filter work?
Dave,
Some folks are getting all worked up over the small stuff.
Reminds me of what I was taught in the Air Force:? measure with a micrometer, mark with a grease pencil,
cut with a chain saw.
I remember a trip I took for several weeks to VA to stay with my grandson while his mother jetted off to EU
for 10 days.? I brought my handheld 2M, but could not hit the repeaters inside with the rubber duckie.? Found
some #22 wire, made a dipole for 2M, thumb tacked it to the wall up as high as I could, made "coax" with
the #22 as twisted pair.? Worked like a champ!
73
Glen K4KV
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On 3/4/2020 12:25, David Eckhardt wrote: In that respect, after working decades above 50 MHz, 630 and 2200 meters is
a relief. Clip leads are not even seen by the RF energy.
Dave - W?LEV
On Wed, Mar 4, 2020 at 4:23 PM DougVL <K8RFTradio@...> wrote:
Aha! Great - I had wondered at the time I read it about the power
capacity of the N type. Since I don't have any, though, I wasn't motivated
to research it. Glad to know the truth now - thanks.
I know a lot of older (tube-type) test equipment used twin banana plugs.
Maybe the development of o'scopes that reached higher frequencies caused
the development of the shielded coaxial connector.
And I'm not sure I should even post this, drifted so far off topic. I do
think the original question was important, and the info about HF
measurements not being so critical of lead lengths for calibration.
Doug
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Re: SO-239 standards for HF Band-pass filter work?
In that respect, after working decades above 50 MHz, 630 and 2200 meters is
a relief. Clip leads are not even seen by the RF energy.
Dave - W?LEV
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On Wed, Mar 4, 2020 at 4:23 PM DougVL <K8RFTradio@...> wrote: Aha! Great - I had wondered at the time I read it about the power
capacity of the N type. Since I don't have any, though, I wasn't motivated
to research it. Glad to know the truth now - thanks.
I know a lot of older (tube-type) test equipment used twin banana plugs.
Maybe the development of o'scopes that reached higher frequencies caused
the development of the shielded coaxial connector.
And I'm not sure I should even post this, drifted so far off topic. I do
think the original question was important, and the info about HF
measurements not being so critical of lead lengths for calibration.
Doug
--
*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*
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Re: Calibration connectors
I solved the problem like this.
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Re: SO-239 standards for HF Band-pass filter work?
Aha! Great - I had wondered at the time I read it about the power capacity of the N type. Since I don't have any, though, I wasn't motivated to research it. Glad to know the truth now - thanks.
I know a lot of older (tube-type) test equipment used twin banana plugs. Maybe the development of o'scopes that reached higher frequencies caused the development of the shielded coaxial connector.
And I'm not sure I should even post this, drifted so far off topic. I do think the original question was important, and the info about HF measurements not being so critical of lead lengths for calibration.
Doug
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Re: Ceramic filter measurement
On Tue, Mar 3, 2020 at 04:12 PM, David Platt wrote: This will give you a high S11 return loss, and
provide plenty of signal to drive the JFET. You _might_ need to pad down the
NanoVNA drive signal to keep from overloading the JFET and saturating the
whole IF chain.
I wouldn't personally want to try fiddling with those filters without a _lot_ of
careful thinking up front... the alignment procedure is probably a whole cave-full
of hungry bears. Mark the starting positions carefully!!! As you say, fiddling with something this complex is unwise; it's said they had to invent a stereo sig-gen good enough to get the lowest distortion and highest stereo separation it could achieve over the full audio spectrum. I want to look at the 19, but reserve an 18 for tweaking, one I did more than 30 years ago. At that time anything worth listening to was over 150 miles away, and it needed better adjacent channel selectivity. I narrowed the IF substantially using its built-in scope, which displays bandpass shape and (with a constant scope horizontal gain) was useful to gauge the change. Steep sides and flat top over the IF passband for a wide range of input signals - the only way to gauge flatness of each stage, as they gain-compressed. When I look
at the next stage of the schematic (the limiter assembly) I see this signal
driving right into the base of a BJT, whose emitter is AC-bypassed to
ground... So, you have that schematic? Let me know if not; I have service manuals for both the 18 and 19. A safety "gotcha" here, though... this IF strip has some gain in it due to the
input and interstage-buffer transistors! The signal coming out of the output
will probably be larger than the signal going in - I'm not sure how much. Agreed! I'm most concerned about the VNA output amplitude, which almost certainly far exceeds even the strongest off-the-air signal. Pad input and output, then reduce as required. Appreciate your feedback, Dave. -- I_B_Nbridgema
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Re: Calibration connectors
Hi John,
This matter has already been discussed by those skilled in the art of calibration.
What's important is that you can use it in short waves, but you said both 2M and 70cm.
Therefore, I would recommend that you purchase a N dad calibration kit.
I bought it on aliexpress for 18 usd at a reasonable price here:
It's cheaper now :D
I hope I could help.
73, Gyula HA3HZ
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Newbie question. I run 2 x 10cm sma pigtails from my nano, onto an external frame. They connect to a back to back SMA <> N Socket. My reason for this is I will use the nanovna-f outdoors a lot, connecting 10mm dia and up coax, so I'm not keen on direct connection to an SMA, with or without pigtails.
Question is, for calibration, can I just use the 3 x SMA calibration connectors by placing these onto an SMA <> N Plug adapter on the other side of the frame, or will the additional distance inside the adapter affect this?
I'd be mainly using this in HF and 2m if this is more critical at higher frequencies, although ideally, I may also need to use on 70cm at times as well.
73
John MM0CCC
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va3rr
Chris K2STP
Aleksander Shalygin
Nbridgema
Gyula Molnar