ScanKing Royal Discone 2000 - 25-2000MHz - Ferrite Core location

[R2000]

Hi,

I have a ScanKing Royal Discone 2000 and want to reduce electro inteferrence.

My simple question is; which end would i place Ferrite Core/s ?

1. At the base of the Antenna, where the PL259 Plug is?
2. At the base of the Antenna, and a second at the end of the wire where the reciever is?
3. Just at the end to the receiver?
4. or one just Centre of the cable that runs between the Aerial and Reciever?

Reason i ask this is, i want to cut interference to a minimum, though do not want to lose valuble interference. One such interference i wish to cancel out is Electrical 240/220V.

I also have the use of a Jim M-75 as a pre-amp, so can separate frequency bands - Nice Pre-Amp by the way!

Also one more thing about this Antenna.

If its capable of Transmit and Recieve from 25-2000MHz (2GHz), is there a specific SWR this should be set too, and at what frequency should this be calibrated too, as im not going on my roof ever hour to SWR into the next frequency.

And one last question:

My old Antenna was a Sigma SE-1300, worked great until snapped off my roof.

Though between the Sigma SE-1300 and the ScanKing Royal Discone 2000, is there any performance difference?

The noticeable difference i see is that the SE-1300 uses hollow Ground Planes, and the ScanKing uses Stainless Steel Ground Planes, which im sure improves the life span. There is also a slight difference between how the N-Type Connector links up to the whip with the SE-1300 and a more stronger connection for the plug.

The SE-1300 when snapped off my roof, every ground plane had a lot of corrosion.

Anyway, my initial question is what is most relevant with the Ferrite Core/s.

ScanKing - Make sure this surface is clean as they come with some sort of glue which interfers with connection, i sanded this smooth.

The SE-1300 Ground Plane - Well corroded.

ScanKing Discone 2000 Centre/Hub

The dead Sigma SE-1300 Hub

Dont know where the whip went from the Sigma SE-1300, just went with the wind.

One other thing, with using Ferrite Cores, will this impact SWR for the worse (TX & RX) ? Im guessing it would improve, though calibration of SWR would be more tedious to make precise? As in where to precisely place the Ferrite Cores on the Cable. Like balancing an Alloy Wheel as an analogy.

 

[Ubbe]

Any metal wire, like coax, will work as a wire antenna and pick up interferencies. A discone would have less problem with this as the last bit of coax to the antenna goes in a metal tube that will more or less ground those interferencies. Down at the receiver it could travel on the coax and into the receiver and it depends of how well shielded the receiver are. Unidens mobile scanners have usually excellent shielding.

You would like to have the core at the point on the coax where the radio wave of the interference are at its maximum. That's impossible to predict so either clamp enough number of cores on the coax to cover 1/2 wavelenght of the frequencies you monitor, or wrap the coax around the core several turns so that the length of that coax will be a 1/2 wavelength of the lowest frequency you monitor.

Interferencies travel on the outside of a coax's braid and the return path of the RF signal on inside of the braid. Having cores could have an impact on the impedance if the braid are thin. Coaxes with dual braids and foil shouldn't be affected.

/Ubbe

 

[R2000]

Ive not installed the Antenna yet, as i had to buy a new one.

Ive now chosen to use RG8 instead of RG58, its mainly receive im aiming for, Transmit is just an option and available.

The main uses for this Setup is solely SDR, i see hardware Radios i.e ICOM, Uniden is an obsolete way of utilising frequencies these days. Though they are of very high quality recievers, but now we have full control over software that controls the hardware, in many ways a single device is limited.

To cover 1/2 wave length of Coax of 10M, what would be the best place/calculated spot to put the Ferrite Core?

The frequencies i will be observing are from 0.5MHz/500Hz - 6000MHz/6GHz

I know the Antenna is supposidly only capable of 25-2000MHz/2GHz, but we know it can pick up any transmission really, just not at a precise calibration.

My thinking is to place the Ferrite Core right at the end, where my Coax enters the property, or am i wrong and it should be right at the top where the PL-Plug connects to the base of the Antenna?

or one at both ends. The Ferrite Cores im using are clampable onto the the Coax, they do not need the wire to twist around them.

See image.

 

[prcguy]

A single ferrite core as you show will do nothing at any HF/VHF or UHF frequency and you would need at least three in series made from #43 ferrite or Laird 26 material to have any good choking at VHF and UHF. Three ferrites will do absolutely nothing at HF and you need a different type of ferrite with lots of turns of coax around it for lower frequencies.

Otherwise, if the goal is to strip off any RFI picked up by things in the house onto the coax you could put the ferrites anywhere after the coax passes by RFI making devices. Placing (the proper) ferrite at the point where the coax exits the house and at the base of the antenna can sometimes reduce noise pickup by the coax a little more than just at one end. The only thing ferrite can do is absorb RF riding on the coax shield, it will not prevent noise pickup by the antenna through the air.

A VHF/UHF Discone like the ScanKing Royal Discone 2000 is an actual antenna from the low 100MHz region to about 800MHz and the whip on top is probably sharply tuned for 6m or 50MHz like most similar Discones. The antenna is not designed for HF reception like anything below 50MHz and is a very poor performer there. It will pick up some HF stuff but the signal levels will be very low compared to an actual HF or SW antenna. It will also not work for transmit except where it is an actual antenna like whatever frequency the top whip is tuned for, either 50 or 27MHz then about 118MHz through maybe a GHz. Above about 500MHz the radiation pattern starts to shift upward and by 800MHz reception will be down probably 10dB compared to the VHF band and higher than 1GHz the pattern is all over the place and mostly nowhere useful.

No antenna made for use over about 500MHz will ever use a PL-259 connector, that is some kind of joke.