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On Tue, 10 Mar 2020 05:54:55 -0700, you wrote:

hi all i have a 80m dipole set for 3.775 Mhz,it seems to work rubbish,ive just done some adjustments,,take a look at the pics of it on the vna,does it look ok,views welcome,cheers m3vuv.ps,forgot to say its 2 80m mobile whips in a dipole config,up at about 12 feet for nvis .

The first 2 pics look OK,
but then you did something wrong to your VNA.
Usually 80 m wire antennas are very narrow
and cannot cover the complete 80m band.
To make it broadband use multiple wire arrangements.


OE8UWW

Ive had this issue a few times on win 7 sp1,seems the windows updates screws the drivers up,normaly reinstall the st whatever it is driver and then it works,not sure on win 10 tho as i hate it with a vengance! 73.

hi all i have a 80m dipole set for 3.775 Mhz,it seems to work rubbish,ive just done some adjustments,,take a look at the pics of it on the vna,does it look ok,views welcome,cheers m3vuv.ps,forgot to say its 2 80m mobile whips in a dipole config,up at about 12 feet for nvis .

The trace capacitance is ~ 6.5 pF before and after the modifications.

The inductance is 0.046 uH. Insignificant?

The PCB is small, 17mm x 25mm, not much trace area/length.

Allison, The only examples I found in EMRFD are for VHF filters on page 3.7...nothing for HF.

Still need to build the 30m filter...

--
Chuck, W5USJ

when I connect it to a laptop using the supplied USB-A to USB-C cable, I get a warning

A bad cable is among the first things to suspect.

From: Pierre Martel

Hi David,

Do you have some information about the maximum dynamic range the pluto can
do in sa/tg mode?
====================================

Pierre,

I've not seen any specifications for that, but here's a quick plot of the RTL-SDR 88-108 MHz bandstop filter compared with a Rigol DSA-815. I would reckon 60 dB at that frequency, and that's with the 10 dB attenuator on the Pluto TX and RX ports.

The plots were made some time apart. I looked on the RTL-SDR site for their response plot, but it seems to be missing....

Cheers,
David
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

From: Leif M

Are any these able to show close sidebands. Like what happens with 1kHz or 100Hz SSB modulation
================================

The minimum receiver bandwidth range is currently 2 MHz, but the Pluto can be used very successfully as a narrow-band receiver so I think this is just a programming limitation at the moment. You could buy the programmer (that's NOT me) a beer or two via PayPal along with with request for narrower receiver spans!

Cheers,
David
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

I have discovered that this happens and everyone tells you the problem has
been solved. But when you try all the fixes, it still does not work! It
seems that the WIN10 virtual comport gets confused by having made many
changes. I don't know exactly why, but I found a site that has a "driver
fixer" and that worked for me.

Here is a link:


Please let me know if this solves your problem too!

Robert M.

Thanks, Dragan - clearly seen on the web page!

Parts ordered...

Dave

Recommended capacity and dimensions are listed on tindie page.

On Tue, 10 Mar 2020 at 01:59, David Feldman <[email protected]>
wrote:

Please excuse this post if it's been covered previously, but with a
nanovna-v2 enroute via tindie, I realized I believe it is not fitted with a
battery by default. Is the battery specification (part number or dimension,
anda any specific additional requirements) available?

Thanks,

73 Dave WB0GAZ wb0gaz@...
(originator of nanovna-users on groups.io, so with precious little time
then left to actually play with the thing!)

On Sun, Mar 8, 2020 at 08:00 AM, Kerr Smith wrote:

Using my NanoVNA I want to measure the impedance (and return loss / VSWR) of
my RF input circuit so I can adjust the windings to get a good match but the
NanoVNA outputs around -13 to -9 dBm, this is too high for the NE602 RF input
which has a maximum input of about -25dBm.

How would I go about attaching the NanoVNA to the RF input of the NE602
without causing an overload?

The NanoVNA output with older firmware is around the levels you posted. With Hugen's latest firmware it goes up to 0 dBm.

Let's assume you are using the older firmware and you want to get a test level lower than -13 dBm. There is a technique you can use to reduce the level being input to the Device Under Test (DUT). What you need is a good 20 dB SMA attenuator like the ones posted below. Connect a short SMA cable to CH0 of the NanoVNA and the other end to the input of the attenuator. Then set your frequency range to the band of interest (like 6 to 8 MHz for your 40M tests). Go into the Cal menu and do a Reset to clear all the cal parameters. Then do a calibration in the normal way placing the short, open and load on the output of the attenuator. When you have finished save to one of the memory locations (1-4).

Now you have calibrated with the attenuator in place and you can measure Return Loss and VSWR by setting your Traces accusingly. The maximum signal into the device, in this case your impedance transformer, will now be -29 to -33 dBm. This "trick" has some inaccuracies compared to the no attenuator method but I find it works well with a VSWR from 1 to 4. It works even better with 10 dB of attenuation but much worse with 30 dB.

Disclaimer: This is not my discovery. I found this technique posted by someone else on this group several months ago. Maybe they will follow up this post with their comments...

Please excuse this post if it's been covered previously, but with a nanovna-v2 enroute via tindie, I realized I believe it is not fitted with a battery by default. Is the battery specification (part number or dimension, anda any specific additional requirements) available?

Thanks,

73 Dave WB0GAZ wb0gaz@...
(originator of nanovna-users on groups.io, so with precious little time then left to actually play with the thing!)

All nanovna-h sold by us have version number marks on the PCB. Since rev3.4, we have also added version number marks on the shell labels.

hugen

In case it matters - version 0.4.0-2-g7c2f745
No version marking on any of the PCBs as far as I can see (I took off the front and back covers).

Kerr,

I have wound these high ratio transformers using FT50-43 and FT37-43 toroids and always found leakage inductance which affected VSWR, Bandwidth and Insertion Loss. I then read about W8JI's experience with BN73-202 and BN43-202 binocular cores. You get better coupling with these and less leakage inductance. The initial permeability (2500) of the BN73-202 is so high that you only need a few turns to meet the minimum 4X reactance at the lowest frequency. So for a balanced input with a 3000-50 ohm match 1 turn on the primary and 8 turns on the secondary would work well @ 7 MHz. The 73 type material has low resistivity so I recommend that you use kevlar wirewrap wire or Cat5/6 insulated wire becasue enamel wire might nick and contact the core.

Hi all,
I bought a new NanoVNA-H on ebay and received it today. It seems to work, but when I connect it to a laptop using the supplied USB-A to USB-C cable, I get a warning "USB device not recognised. The last USB device you connected to this computer malfunctioned and Windows does not recognise it". I've tried connecting many times, different ports, rebooting, and a different laptop, but always get that message and the device shows up as "not working" in device manager.

I had a quick look at the board, the connections to the socket and soldering of the processor look OK, no shorts that I can see.

Has this been seen before, is there a solution or do I need to buy another one?

Thanks for any advice.

Hi David,

Do you have some information about the maximum dynamic range the pluto can
do in sa/tg mode?




Le dim. 8 mars 2020 à 07:43, David J Taylor via Groups.Io <david-taylor=
[email protected]> a écrit :

For those of you with an ADALM Pluto SDR, here's a 70 MHz - 6 GHz spectrum
analyser & tracking generator:



Looks very interesting. Anyone played with this software?

Cheers,
David
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

Ground loop due to residual inductance.

EMRFD has a detailed example of what that is and how it can degrade a filter.

Experimental Methods for RF Design, ARRL press.

Allison
-----------------
No direct email, it goes to bit bucket due address harvesting in groups.IO

Any idea when it is available at Ebay. I am lazy and would not want to open one more account to somewhere.

Are any these able to show close sidebands. Like what happens with 1kHz or 100Hz SSB modulation