Posts by lz2ilr

so after recalibrating the vna with the short lead, all levels are correct!

tomorrow the ugly thing goes back up, and maybe you will hear me.

73

im a bit stuck for calibration as i only have the standard set of short, open, 50 ohm. to put them on the end of the cable i need a f/f adaptor and that changes the readings too.

on the feed it is n type with an sma adapter, worse still the signal going from house to dish+anp is rg6 with f to bnc, bnc to sma both ends.

far from perfect but working with what i have. parts take weeks to arrive as standard.

im going to try calibration with a female female adapter and see what it says.

any suggestions of good youtube about this kind of work/layout/etc for these frequencies?

great suggestions lads but im going backwards fast: just changed the sma lead to the feed from 20cm to 10cm and now all my swr is way out again. i suppose that is normal at these frequencies

Quote from DC7KG

Hi,

here you can see the beam width: https://jcoppens.com/ant/helix/calc.en.php

brilliant. now i can tune my beam to my dish.

my 817 is working fine now , and i am hoping to get a mixer and vco put together as my upconverter and rtl sdr is doing fine for downlink, although i do want another mixer just for rx, or maybe modify lnb if its possible to get an output in the hf area using 27mhz cystal in place of 25 mhz.

one day i will get a pluto but roof repairs are first priority.

i also like the esp32/lora 2.4ghz qrp projects that really push the cost barrier to uplink and they do feldhell which is a nice mode

so adding the 40db amp raised the current draw from 350ma quiescent to 850ma with nano vna input. i added a bp filter before the pa that incurred 5db loss. win!

i am wondering if my 4.5 turn helix should be shortened to fully illuminate my 2.4m dish because if its too directional the signal will only bounce off the center of the parabola and end up back in the antenna or be obscured by the ice cone and all the amp gubbins im going to mount in its shadow (prime focus)

so i will feed the nanovna output -17dbm into this amplifier with 40db gain, but that would give 251mw output, and output max is 100mw, so i insert coax loss from 20m rg6 and this amp then gives 20mw output. add 13db gain from the pa and i get about 400mW at the antenna. by maths are too rusty to do it longhand so i used various online converters and calculators and no doubt pigged it up a bit, so if anyone still fresh with numbers wants to correct me, please do so.

with the 2.4m dish i think 400mw feed should definately get me a scratch on the waterfall, am i right? i think the dish gives 33db gain.

other options would be adding an amplifier before the coax as well as one after to hopefully get 4w to the feed and reduce noise from the amp

nice setup but i couldnt even afford the coax

many thanks, i didnt realise the vna output was so low. i guess i should read the manual and do some maths. i do have a 40db and 20 db amplifier which should get a better drive level. i also have one of those cell tower palletts for 2x 200w but im not touching it until i can safely deal with a couple of watts for obvious reasons.

my end goal is building an upconverter from cheap off the shelf parts as a training exercise. does anyone have suggestions for a better vco for 2.4ghz? budget is pretty tight so no gps locked unit yet. or might the ysgm232508 actually be useable if its put in a temperature controlled box? i have a 2.4ghz band pass filter but again i am unsure of how to test it using the vna and i know off the shelf parts are not always the spec claimed. i really dont want to be 'that guy' who messes things up for others with a dirty uplink

i am trying to test a simple setup with a helical antenna, hs242036t1 4w amp and nanovna as a cw source. i had the amp and feed (snowcone) mounted to a 2.4m dish and can verify rx. i was hoping to activate the setup for a second to see a 'scratch' appear on the downlink waterfall but nothing showed. also the current draw from the amp 300mA did not rise on the nanovna input. the helix showing 1:1.3 at 50.3 ohm. the only other microwave source i have is a ysgm232508 vco but im thinking this will be too unstable.

so can someone please suggest ways to a: test the amplifier using the nano vna v2, and b: use the nano vna to verify the quality and frequency of oscillator, c: test the 2.4ghz bandpass filter.

sorry if these are dumb questions but i am new to working with anything above 70cm, and of course i dont have funds for high tech test gear.

ps. rtl sdr with tcxo is rx and only good to 1.7ghz