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active antennas on ebay?

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ModelTrainGeek

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I've been wanting to get a short wave again.. but being in an small apartment, there's not a lot of room for a long wire antenna (balcony is only about 10 feet long, and the apt manager is not that cooperative/helpful a person)
so i looked on ebay and found a few inexpensive active antenna from china.. I'm just wondering is anybody has tried them? they run around $25...
 

ka3jjz

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You'll have to do better than that - model? Brand name? Both Degen and Kaito have had active loops out there for some time. I think we have a couple of loop-related reviews in our loop antennas wiki.

The king of all active loops is the Sony AN-LP1, by all accounts. I understand that does show up on eBay from time to time. However there are some homebrew loops which also work quite well, as I understand it. And there is the Carpet Loop, which is a nice starter-type project.

73 Mike
 
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ModelTrainGeek

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I was trying to avoid posting an ebay link.. one is item number: 270511493113
KESTREL W31MS
 

k9rzz

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$25 shipped from Hong Kong and it comes complete with "Soft Antenna Lopps" !

He's a Power seller with good feedback.
 

N0IU

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As long as you are on eBay...

Another type of antenna you might want to consider is one made from 2 Slinkies! No, its not a joke! Just search for "slinky antenna" and you should get at least 50 results. I have one made of brass, but since you are using it indoors, you can save some money and get a regular one since weather (rust and corrosion) will not be an issue.

As soon as the weather warms up (so where is this global warming I keep hearing about?), I plan on putting mine up outdoors, but for the mean time, this is how it looks indoors close to the ceiling. I just used some hooks on each end and one in the middle. You have to run some sort of support (I used monofilament "weed eater" line) so the Slinky doesn't droop. You will also need a length of coax to go from the bottom of the "Tee" in the middle of the antenna to your radio.
 
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ka3jjz

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That 'Kestrel' looks like a Chinese knock-off of the Kaito KA33- the system diagram looks to be almost identical to this one...

Kaito KA-33 System Diagram

The Slinkies are controversial - some folks say they work OK, others say it's total junk. One of the things that you need for this is room - it seems to work better if you have the room to stretch it out. Otherwise all you're doing is tuning 2 huge coils. Not very efficient. There are some reviews, I think, in eHam about these kind of antennas.

If all you're doing is listening and in a hostile environment like a condo with a HOA (I've haven't heard of one that didn't have one...) or an apartment, loops are a much better bet, since they can reject certain kinds of noise, and at least for some, you can move the receive element around to find a quiet spot. They will never ever beat a good outdoor antenna, but for some (like me) that's just impossible.

73 Mike
 

k9rzz

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Those diagrams are pretty similar. I guess it all depends if you want your antenna made of "Soft Antenna Lopps" or "Loops". LOL
 

ka3jjz

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Y'know for the price, it might not be a bad deal just to tear it apart to experiment. If you could use a much larger loop, and increase the length of the lead between the amplifier and the controller (which evidently has some sort of tuning or matching), it might be well nigh ideal. I'm unsure that using a larger loop might not be tunable with such a small capacitance, but it's worth trying....73 Mike
 

ModelTrainGeek

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I just tried hooking up about 10 feet of wire (14 gauge) to my old portable radio that has shortwave bands below 22 MHz. I managed to pick up a couple religious programs around 7MHz (it's a simple tuner so it's not very exact) and a lot of stations that were a continuous tone (kind of a weird hollowing sound) but from my radio's point of view had no meaning but making that tome. I couldn't find the time stations like I remember doing with this radio many years ago as a kid. I And I for a few broad "signals" that just sounds distorted like being over driven, I'm guess local AM broadcast stations bleeding in it's tuner.

Has was goes on on these frequencies changed so much these old radios are useless? or does it sound like interference? I'm wanting to track down an old Realistic DX-160 like I had years ago, but if noise is all I'm getting in this apartment, I may as spend the money else where..
 

georgew0819

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Has was goes on on these frequencies changed so much these old radios are useless? or does it sound like interference? I'm wanting to track down an old Realistic DX-160 like I had years ago, but if noise is all I'm getting in this apartment, I may as spend the money else where..
The old radios still work fine even if they lack the bells and whistles of newer radios (usb, digital freq readout, scanning and such). I've got an old boat anchor, Hallicrafters S-38E and I still find lots to listen to. I've managed to hear stations in China, Japan, Russia, South America and here in the US just using a carpet loop.

In fact in my humble opinion I think that turning a dial bit by bit and working the bandspread and homemade antenna to hear that distant station is a lot more satisfying than just punching in a frequency on a keypad to find various stations.
 

blinddog50

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Does anyone live above you?
If not you can go to Sh*t Shack and get some very small nylon wire clips that has adhesive on them that you can stick to your wall.
Place the clips about every 3 to 4 feet along where your wall and ceiling join together.
Use # 22 copper wire and run it along though the clips.
Attach it to the Hi Z connection on your radio.
Use a balun if necessary.

Cheap and discrete.
 

ka3jjz

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I just tried hooking up about 10 feet of wire (14 gauge) to my old portable radio that has shortwave bands below 22 MHz. I managed to pick up a couple religious programs around 7MHz (it's a simple tuner so it's not very exact) and a lot of stations that were a continuous tone (kind of a weird hollowing sound) but from my radio's point of view had no meaning but making that tome. I couldn't find the time stations like I remember doing with this radio many years ago as a kid. I And I for a few broad "signals" that just sounds distorted like being over driven, I'm guess local AM broadcast stations bleeding in it's tuner.

Has was goes on on these frequencies changed so much these old radios are useless? or does it sound like interference? I'm wanting to track down an old Realistic DX-160 like I had years ago, but if noise is all I'm getting in this apartment, I may as spend the money else where..
There are certain things that you can do to reduce the noise, but in an indoor apartment, your options are somewhat limited. Things like these new CFL bulbs, some wireless routers, kitchen appliances...the list of things that can cause noise is likely endless...

As I've mentioned before, probably the most effective antenna you can use indoors are loops, since they tend to reject some noise types. There are other tricks, perhaps less well known - hertzian talked about putting a couple of 20 foot radials on the ground lug to provide a RF Ground (there's no way a cold water pipe can be a good RF ground - particularly if you are up on a 2nd floor or higher...), put some filtering on the AC line, using coax on an antenna (note that it probably won't work quite as well on portables, since most of them are looking for a hi impedance input). If you are using a portable, choke off that wall wart. Noise is the enemy on HF, and in an indoor environment, you can cut it down, but I don't believe you will ever get rid of it entirely. 73 Mike
 

ModelTrainGeek

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I'm on the 8th (top) floor. I'm going to start trying some loops and such inside today.. The apt has a suspended panel ceiling, so I'm thing hanging the wire by clips a 90 degree crossing the supports.

I already have my radios on a TrippLite IsoBar Ultra. I did track down that my X-10 lamp controllers are a source of noise if on.. My wifi router (Linksys WRT54G) is on the other side of the room.

When I get a day the weather isn't quiet so cold and nasty, I'm going to try a wire from side to side of the balcony outside.. This high up it probably will go unnoticed.. You can't even see my little ground plane scanner antenna mounted above my satellite dish :)


thanks for the info guys.
 

ka3jjz

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You'd probably be better off if you wrap the perimeter of the balcony, rather than side to side. Bring the two ends down to a 9:1 transformer, then coax to your receiver. Even a crude loop like this ought to outperform an antenna indoors in at least some situations.

Use clear or white plastic wire and it will be darn near invisible. Nice and thin....73 Mike
 

radioaction

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Kestrel, Degen,Kaito active antennae

They are identical - same factory, different market brand. The loop will work as advertised 4-22 mhz, but this should be read as meaning both noise and frequency voltage increases, not intelligence.The strongest reason to use a loop is totally lost..the loop does not null because the feed is badly mismatched.The variable capacitor voltage diode has a low Q, suffers from DC-DC noise at the primary and for several harmonics above. The supplied 15 ft of stereo cable is not shielded, and acts as a noise pickup as well. There have been attempts to modify the electronics, including adding shielding to the loop, and feeds, but the single transistor amp, the badly designed feed, and severe DCDC harmonics, has caused abandonment of this offer.
 

g5turbo81

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Active Antenna

Mike is right, Loop antenna's work considerably well for the time and money spent to make them. In my own situation, I use 2 copper loops for AM DX and SWL. I use a Wire loop for NDB's in LF. All work incredibly well for me with a low noise floor, especially when I hear others having issues with noise 500 khz and below.I use two (much) larger loops for transmitting on 20 and 40 meters. The results are impressive. Compared with my DB18E, the loops for xmit are not as good, but most other antenna's I have/had aren't either. Search the internet, and you will find plans for many kinds of loops. Anyone who I have ever sold a loop to, has loved them from jump street.

Also, When I lived in an apartment, I ran a wire from the downspout of the Gutter to an antenna tuner..Worked well... The MFJ Active Antenna worked well for me provided I used and external antenna with it. I've hooked loops up to the MFJ, and it does a good job. Find some good sized Cardwell Capacitors, and have fun with it...Thats what it's about.I've tried, and Have countless antenna's and It's always a blast to compare 5 antenna's to see what gets the best signal.

73's

Matt
 
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