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Best Antenna Combinations?
Posted: Thu Jan 12, 2017 7:42 am
I want to buy some more dongles with HF upconverters before I move up to the SDRPlay and Airspy/Spyverter combo & am wondering if the Austin Ferret for 30 MHz+ & the Apex 303WA-2 HF antennas would be suitable or would they be overkill for entry & mid level SDR? I'm running my dongle off a glass mount CB antenna designed for vehicles but I attached it to a window in my house with excellent results considering & zero overload. I clearly receive 11 meter CB up to 161 MHz, reception downgrades considerably at 460 MHz & can barely receive the control channel buzzing on the local county 800 MHz PS trunked system. Thanks all.
Re: Best Antenna Combinations?
Posted: Thu Jan 12, 2017 11:18 pm
It is very hard to pick an antenna for someone else. It is like asking what house do I want?
The thing is, you have to ask your self some basic questions. What frequencies do I want to receive and of those which do I favor and at what distance? What is my budget? What is my situation for mounting and room available?
Let’s start out with what you have given us. An up converter to be used below 30 MHZ.
While a vertical will work well and the Austin Apex 303WA-2 HF has good reviews. At $120 is it what you want. It is a rather questionable declaration to make and pull off any kind of realistic performance as the 1/4 wave length at 30 MHZ is approximately 10 foot and it has a total length of only 6 foot.
A vertical favors signals from a low approach angle and will show some improvement over a low horizontal at low angles. The above mentioned antenna might be OK for most RTL-SDR applications as the front end of the RTL-SDR is easily overloaded however don’t expect it to be a superior antenna for HF work. A simple horizontal of an adequate length will deliver stronger signals at the HF frequencies for considerably less $ but might overdrive the RTL. This can be helped with filters but at additional cost and or effort. The low horizontal also favors higher angels of signals approaching the antenna. This will be at a cost in signal strength for distant signals. However a longer horizontal will almost always have a stronger signal strength on the HF frequency. It can have a worse signal to noise ratio. Making it harder to pick out the desired signal. For a newer person. I would suggest a horizontal dipole or long wire. If you have the room and sports. If you want resonance use traps and cut the antenna appropriately, Use filters to help with the strong signals if the RTL-SDR has problems with a over driven front end.
As for VHF and UHF Austin Ferret for 30 MHZ+ is a different animal all together. It has good reviews and has built in traps for 8 frequencies. The questions come in. Is the 8 frequencies the ones you want. Will it outperform a discone? Is the $250 price tag realistic. If you have the $ to spend and the 8 frequencies it is built for are what you want. It might be? If $ is a consideration and versatility a discone might be a better choice with an LNA amplifier and filters. I for one favor the filters, amp and discone but again it is like saying what house do I want.
Now the question of the up converter. The Spyverter has excellent specifications and I can say nothing bad about it. I am suer it is a very fine product however I have never owned or used one.
I use a Ham-It-Up converter and am very satisfied with it. I chose this converter for the built in noise source. This is something that you will have to decide is some thing that you want or not. I personally find it to be one of my most valuable pieces of test equipment. If you should deside on the Spyverter you can buy a aftermarket noise source but in my case it would have added cost and complexity. This is again the question of which house.
The one bit of advice I can give without reservations is. Do some research, ask some questions and do some planing before spending any real $ on anything. A well thought out setup will always perform at its best where a costly one might just cost a lot. In any event choose wisely and enjoy the great hobby.
Re: Best Antenna Combinations?
Posted: Fri Jan 13, 2017 8:18 pm
A few things to keep in mind:
* Every antenna is a compromise.
* Unless directionality is preferred, it is rather difficult to outperform a half-wave dipole that is properly built for the desired band.
* A dipole is really cheap to build at home. Keep in mind also that dipoles usually work fairly well (with slight changes in their pattern) at odd harmonics. So if you build a dipole for 7 MHz it will also receive well at 21 MHz.
* A long dipole (e.g. built for 3.5 MHz) with an antenna tuner is also a pretty good solution most of the time.
* Pretty much the only downside to a dipole is space. An 80 meter dipole is going to be about 120 feet long. Note however you can bend the dipole to a certain extent, so if you need to zig-zag it through the garden that should be OK. Also, any dipole that is less than about a quarter-wavelength high will tend not to perform as well. So again for an 80 meter dipole you need to run it through the tops of trees or buildings to get proper pattern.
* Traps (which the Ferret seems to use) are generally not terribly lossy. A trap dipole is a decent solution if you don't have the space for a full-sized dipole.
* Note that you can use traps to get multiband functionality.
* You can also build a fan dipole for multiband functionality. Basically these are a bunch of dipoles with a common feed point.
* Antennas that use loading coils or capacitance hats to shrink their size are usually not very efficient.
* Antennas that use various clever tricks to be broad-or-multi-band (for example a G5RV) are of debatable utility.
For VHF (really for 11 meters and up):
* You pretty much need a vertical antenna if you intend to do general monitoring. Very few applications at VHF use horizontal polarization (weak signal ham for example).
* If you are using vertical polarization and do not care about things that are directly above you (satellites, nearby airplanes) you can use a 5/8th wave antenna or J-Pole. These typically have patterns that favor the horizon more than a quarter-wave vertical does.
* A discone is a great choice for VHF and above, but can get damaged easily in a storm.
* The Austin Ferret does not look like a bad choice, but for me, spending $200 on an antenna is a hard call. Generally I don't buy antennas unless these conditions are true:
** It has some special functionality or quality that warrants its use (as opposed to a dipole or 1/4 wave vertical).
** Its design is too complicated for me to build myself.
** It is on sale (or used; have you considered attending a ham fest or swapmeet to see if anybody has an antenna they are selling?).
If those conditions are not true then I usually just build my own.