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ACTIVE BROADAND ANTENNA How do I improve HF performance?


obrianboru@...
 

Thanks Simon!
Good advice on G3TXQ,- Steve's work is my bible for chokes, Steve was a great researcher and an equally great teacher.; explaining complex concepts whilst avoiding the esoteric jargon !

The antenna seems to receive as well, maybe even better, than my earthed, choked Miniwhip on HF and it does an excellent job on VHF and UHF.

RFI... same here with this shack, it's full of computers, monitors, sat TV, quad HiFi, battery chargers and desulphators (the list of gubbins goes on)  LOADS of switch-mode PSUs generating a tsunami of noise, Even short 12v DC cables from my main clean PSU collect rf trash on their way to units! I tried using earthed and shielded cable to those devices with no success but I luckily found a bargain bunch of small mains-filters which do an excellent job of cleaning rf off those shack DC cables.... but the real solution of course is for me to kill the sources of the noise. Wiring new power cables to 12v devices from my clean PSU and finding old linear PSUs or even batteries at the other required voltages, will probably be cheaper than getting another mortgage to buy the mountain of ferrite this place needs!
I'll experiment with your helpful suggestions,
73 Jeff 2E0CIT


Simon
 

Jeff..

adding chokes to coax will not effect inductance of antenna..
if you wish to do well do as Chris says..but you can wind turns of coax around 31 and 43 etc rings..

see g3txq common mode chokes for good designs..the idea is to get high impedance to common mode on coax at frequencies you use..
so if you just listen 1.8-7mhz then use 31 type..if you use 1.8-30 then you need 31 and 43 types etc..

i really only use loops for 1.8-7 so i use many turns around ft240-31..overkill for rx as good for 1kw but works well..( oh its using ptfe coax.)

also doing same at rig end is good too..and even  half way down coax if you can..

do same to power cables too if you really want to clean up smpsu noise etc in your rx..

my place looks like a ferrite ring shop! 


obrianboru@...
 

Thanks Chris. I'll fit 43 and 73 clip-ons as you advise, I assume that making more than one turn through the clip-ons to increase common mode choking at HF might add unwanted inductance and upset the VHF UHF response of the antenna, ...but I'll experiment !
73 Jeff 2E0CIT


Simon
 

Steve

May I suggest you remove your phone number asap..

This is an open group..

Simon


Chris Moulding
 

We stopped manufacturing the Broadband Active Antenna at the start of the Covid-19 lockdown.

During the lockdown I took the opportunity to re-design the antenna so that it will work directly from a 5V bias-T such as that in the SDRPlay receivers.

The prototype works really well and we are about to make the first batch of the new design. The manufacturer of the GRP tube we use for the antenna has not re-started production yet so I've ordered tube from another supplier but so far the promised delivery is two days late!

I've not worked out the final price yet until the first batch is built and tested and I know what shipping materials are needed.

I've already got a waiting list for the new antenna so we expect to make a second batch soon after the first one.

I'll post on the website and on this forum once the antennas are ready for sale.

Regards,

Chris


Chris Moulding
 

The later versions of the original Broadband Active Antenna had common mode chokes on the coax feed inside the antenna to stop RF noise from the coax cable reaching the amplifier in the antenna.

To get the same performance I would suggest using two clip-on chokes on the RG-58 feeder cable close to the antenna. I would fit a 43 grade ferrite closest to the antenna with a second ferrite of 73 grade ferrite next to it. Using two different grades of ferrite material improves the frequency range of the RFI suppression and is also very effective in other situations where ferrite is needed.

Regards,

Chris


obrianboru@...
 

My first posting here...I think I maybe posted earler it in the wrong place .....duuuh ....so here it is again!

I have the earlier version of this excellent antenna.It does a great job on UHF and VHF and I'm about to test it on HF.

http://www.crosscountrywireless.net/broadband_active_antenna.htm

Chris states he redesigned it to make it more efficient on HF by adding a new ferrite.
I would appreciate advice as to how I might modify my earlier version of this antenna  to achieve the same effect; I assume the ferrite on the later version helps to cut common mode current on the outer sheath of the coax and of course reduce unwanted rf pickup by it too.
Any info on the best type of choke I could add....ferrite type...31,43,73, and windings, etc., would be very welcome.
73 to Chris and all from Jeff, 2E0CIT