Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

The Lounge A place to talk about almost anything but politics and religion.

No RF gear here?
No RF gear here?
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 29th June 2020, 01:57 AM   #691
benb is offline benb  United States
diyAudio Member
 
Join Date: Apr 2010
Geez. I suppose for the price I could work with an upper limit of 1.5gHz. If I get a 5G design job I'll have to look for something else.

Seeing that I start to wonder how Agilent/Keysight/Tek/whoever-they-are-thesedays stay in business.
  Reply With Quote
Old 29th June 2020, 11:29 PM   #692
AnalogJoe is offline AnalogJoe  Mexico
diyAudio Member
 
Join Date: May 2019
Quote:
Originally Posted by Tubelab_com View Post
I got one of these "Nano VNA's" last week.

NanoVNA-H Portable Vector Network Analyzer 10KHz-1.5GHz MF HF VHF UHF Antenna | eBay

I can confirm that it works as expected with a few known loads that were lying around. I have an HP 8753C, but it is rather impractical for some outdoor antenna experiments. I will do a comparison between the large, heavy and expensive HP and the $80 handheld unit in a couple weeks when I get back from a road trip.
Try using the software Nano VNA Saver
  Reply With Quote
Old 29th June 2020, 11:30 PM   #693
AnalogJoe is offline AnalogJoe  Mexico
diyAudio Member
 
Join Date: May 2019
Quote:
Originally Posted by benb View Post
Geez. I suppose for the price I could work with an upper limit of 1.5gHz. If I get a 5G design job I'll have to look for something else.

Seeing that I start to wonder how Agilent/Keysight/Tek/whoever-they-are-thesedays stay in business.
Just saw a Keysight PNA on e-bay for $380,000 used!, the thing can go up to 65GHz but still you can buy a house with that!
  Reply With Quote
Old 4th July 2020, 02:42 PM   #694
w5jag is offline w5jag  United States
diyAudio Member
 
Join Date: Feb 2007
Location: Arkansas
Quote:
... The tiny Inductors are Murata LQW18A series High Q 0603. (those that look blue-ish.) The shortwave inductors are 1210 or 18?? from Coilcraft or EPCOS/TDK. They are not yet on the board.
I am not geting satisfactory results using SMD inductors in HF filters as constructed on these SMD prototype boards. I'm guessing that at some frequency the pads are going to have undesirable stray capacitance to ground, but it dosn't seem to be an issue at HF ( so far ). I'm doing something wrong, but I don't know what it is.

I built a chebyshev 3 pole low pass filter, - 3 dB cutoff predicted to be 30 MHz. In fact, the same low pass filter built point to point on the perforated board in the early up conversion experiments, so a known to work filter. I built it with 0805 ceramic caps, and the generic 0805 cheap china inductors that can be seen in the picture. I terminated each end with a 47 ohm 0805 resistor to force an impedance match. The calculator is at wa4dsy.net

As measured with the RP, the result was dismal. It had a low pass characteristic, but nowhere near what the filter program predicted, the roll off began about 10 MHz early and was very weak, even by three pole standards, really just a gentle slope. To eliminate the crap cheap china generic inductors as the problem, I built another with good quality EPCOS/TDK inductors ( surplus, but from a reputable vendor - I'm sure they are genuine parts ) but the results were still terrible. Better, but still terrible.

I removed the Epcos inductors, and subtituted inductors I wound on T-25 (red) cores, and remeasured. The 30 MHz predicted -3dB cutoff measured at 28.75 MHz. The program predicted -10 dB at 40 MHz, and I measured -15 dB. 50 MHz was predicted as -15 dB and I measured - 20 dB. I could probably tweak the toroids to get -3 dB at the predicted 30 MHz, but the point is that the toroids work, the SMD parts don't, and I don't understand why or what I am doing wrong.

So far I've fooled around with molded conformal inductors, SMD parts, and toroids, and the only thing that works as predicted in a filter circuit are toroid cores. As I've stated before, I'm aware of Q, but am not going to pretend I understand it. I would have expected the Epcos parts to be sufficiently high Q, maybe not like a toroid, but good enough to behave in circuit somewhat like predicted.

I think I am about ready to join the starter VNA club. I can't find anyone stateside that sells the VNA module for the Red Pitaya, so I may get one of the nano vna's. It seems there are several different variants of those.
Attached Images
File Type: jpg IMG_20200704_084915235.jpg (604.6 KB, 23 views)
__________________
Win W5JAG
  Reply With Quote
Old 8th July 2020, 03:02 PM   #695
w5jag is offline w5jag  United States
diyAudio Member
 
Join Date: Feb 2007
Location: Arkansas
While I figure out the CW keying thing, I decided to build a fast and simple medium wave broadcast band receiver. Since the transmitter test jig has a very wide range, if mediocre, oscillator and power supplies available, it made sense to use it as the base.

This receiver strip is a rebuild of the early up conversion experiments, without all of the drama, from the beginning of this project.

The front end is a simple three low pass filter good to about 28 MHz. The mixer is an SA602, the input is single ended, the output is sort of balanced through a tuned circuit. The mixer noise is probably the upper frequency limit of the strip. The transformers are those nominal 0.2 microhenry transformers we discussed back whenever. The xtal filter is one of the 7.5 Khz two pole ECS monolithic devices. The first picture is the mixer output tuned to a local broadcast station with about twenty feet of wire for the antenna. About the only thing the RP can see at the IF is the modulation peaks. The LO bleed through predominates. Recall the LO is coming into the board at - 2dBm to simulate the xvtr board output for building TX strips.

The IF is an NXP BF1105R dual gate MOSFET. This is an unusual device in that it is an enhancement mode device, and has all of the biasing components on the chip. It is very easy to use, so far I have only smoked one of them. It is a low voltage device, with a max Vds of 7 volts. They're serious about this spec ... . As of a few days ago, Mouser was still selling them.

The red wire coming in separate from the test jig is from an adjustable power supply so I can see the gain response to get the AGC right. It looks like 2.7 volts on gate 2 is about max gain, and gain decreases as gate 2 voltage decreases. I can't tell how much gain the IF has. Before the BF1105, all the RP could see were the modulation peaks; after the BF1105 the station carrier is sitting at a solid -65 dBm. I am using 5 volts on the drain. The extra tuned circuit has eliminated the LO bleedthrough. Pictures 2 and 3 are the wide and narrow view of the IF output, respectively.

I will hang an SMA connector off the IF to use with the RP for newbie SDR.

The transformers are tunable, but I don't have and can't find a diddle stick to fit the slugs. They could be tuned to resonance with a trimmer cap, and I have suitable SMD trimmers, but I measured one of them as they come out of the strip, and picked a capacitor to resonate at 45 MHz. I used the Si5351 and the peak hold feature on the RP to sweep the IF from 44 to 46 MHz and I got it almost dead on resonant at 45 MHz. It looks like the usable low frequency response of the rcvr will be in the range of 150 Khz. I believe these transformers are ham diy usable for both 6 and 2 meter tuned circuits.

The stuff at the end of the board is a try at a transistor infinite impedance detector. It may or may not work. It didn't work when hooked to the mixer output, but that may have been because there just wasn't enough RF there to demodulate.

If it works with the IF output as is, I may leave it alone, add an AGC amp and an LM386 and call it done. Or I might add another IF stage, and / or a down conversion. There is as lot of room left on the board.

A lot of folks seem to package simple stuff in altoid cases. I find them very useful for safe storage and transport of these 50 x 80mm breadboards when they are not in use.
Attached Images
File Type: jpg 45 MHz mixer output.jpg (79.8 KB, 14 views)
File Type: jpg 45 MHz BF1105 IF wide view.jpg (79.8 KB, 13 views)
File Type: jpg 45 MHz BF1105 IF zoom view.jpg (81.0 KB, 13 views)
File Type: jpg 45 MHz IF response.jpg (77.5 KB, 13 views)
File Type: jpg board 2 (1).jpg (132.0 KB, 11 views)
File Type: jpg board 2 (2).jpg (160.8 KB, 7 views)
File Type: jpg altoids storage.jpg (113.3 KB, 7 views)
__________________
Win W5JAG
 

Reply


No RF gear here?Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Where to get audio gear? kuer Everything Else 0 18th April 2015 06:38 AM
Available Gear GrampasStuff Swap Meet 0 10th March 2011 07:22 PM
used gear site Jim Leach Everything Else 0 2nd March 2011 07:43 PM
Laser Pickupīs M52103FP RF-Amp instead of older CX20109 RF-Amp Salar Digital Source 2 25th July 2010 05:44 PM
I am looking for the following gear ....... musicprodusa Instruments and Amps 0 26th November 2006 08:22 AM


New To Site? Need Help?

All times are GMT. The time now is 02:01 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio
Wiki