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Author Topic: inside whip antenna - how bad? alternatives?  (Read 2051 times)
N1KCG
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« on: March 08, 2013, 05:16:43 AM »

am playing around with an inside whip antenna. just for recieving digital PSK31 signals. it is a ten meter whip.  attached to an old but good radio.

noticed that on AM shortwave testing I was getting poor reception, and getting just as good with a cheap handheld shortwave digital receiver.

is a whip one of the worst antennas for reception?   or is it normal to just have poor reception on shortwave.
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K5LXP
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« Reply #1 on: March 08, 2013, 05:53:11 AM »

It is normal for poor reception with an indoor antenna.  A poor antenna outside is better than a great antenna inside.


Mark K5LXP
Albuquerque, NM

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K0OD
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« Reply #2 on: March 08, 2013, 07:22:20 AM »

"am playing around with an inside whip antenna."

Inside what? A wood frame house? Perhaps not terrible for PSK or SW broadcast. I used to live "inside" a massive high rise concrete and steel apartment building that was almost impervious to RF. Luckily I had a balcony on the 18th floor which helped.

Your listening problem may be noise not the antenna. 
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N1KCG
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« Reply #3 on: March 08, 2013, 07:25:56 AM »

yes its wood frame, second floor in a landscape of flat land for miles.

so I should look at the noise floor and monitor what is the average level, compared to what?  what are the typical noise floor ranges that people get, inside buildings?
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K1WJ
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« Reply #4 on: March 08, 2013, 07:32:34 AM »

Ideal short wave antenna could be let's say 120ft to 240ft long - how long is your whip - 8.5ft at the most. Antenna's outside work better. Put up a 75m dipole at 119ft in length with the apex 33ft off the ground - I bet your short wave is alot better - even a 75m dipole at 6ft off the ground will smoke-check your whip in the house. Any noise floor above s-3 is bad in my opinion. I'm lucky to have always had a low noise floor - hope that dont change any time soon.
73 K1WJ David
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K0OD
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« Reply #5 on: March 08, 2013, 08:04:37 AM »

Quote
yes its wood frame, second floor in a landscape of flat land for miles

That sounds simple and perhaps not too bad. I also used to live on the second story of a wood frame apartment... not far from a gigantic power distribution station. My s-meter remained at 20 dB over 9 for hours! No simple antenna would cut that RF mess. So I quickly moved the ham stuff to my business location, which was still noisy but better.

If the problem is noise, that could be coming from within your dwelling (switch off your power at the box and see) or from a neighbors.

"Typical noise" depends on a bazillion things. You haven't mentioned the bands you're interested in. On the 160 meter band, S9 QRN might actually be quiet! Noise is a signal so high noise is not always a bad sign.

Don't blow money on costly fad antennas. Perhaps test an indoor dipole for a higher band like 15 meters. Or hide a thin wire antenna outside, maybe under the roof eaves (assuming it's restricted rental unit). You should be able to do some transmitting too.   
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KX8N
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« Reply #6 on: March 08, 2013, 08:48:09 AM »

I've worked inside apartments for almost 10 years total. Obviously if you can get something - ANYTHING - outside, then you're better off, but of course that isn't always practical. Where I live right now, there is no possible outside answer. If it has to be inside, go as high as possible, such as your attic. In my own instance, even that's not an option. If you can get some kind of antenna near a window it might help slightly. Otherwise, any antenna is better than none. I personally haven't found a good inside option for working under 2 meters. Then best you can do is experiment. Even if I did use an antenna that works great for me, it might not work great for you. Get the whip and just try it. If that doesn't work, try some form of dipole. Loops are supposed to be good, but they have a narrow bandwidth, though if you're parked on a digital signal for a while, that might not be much of an issue.

Good luck and whatever you do, don't give up! You may stumble across something that works pretty well!

Dave
KX8N
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WB6BYU
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« Reply #7 on: March 08, 2013, 09:59:39 AM »

Quote from: N1KCG

...noticed that on AM shortwave testing I was getting poor reception, and getting just as good with a cheap handheld shortwave digital receiver.



Many short whip antennas for receive include a preamplifier at the base.
That allows a 30" whip to work as well as a much longer antenna.

What type of "10m whip" are you using?  A loaded mobile antenna isn't a very good
multiband antenna, while a full length unloaded whip might not be too bad if it
is matched for the band of interest.  This will probably work well enough down to
10 or 12 MHz.  And don't forget your ground system will be important to good
performance, too.

If you are really using a "whip that is 10m long" (which is unlikely to fit inside
most houses), rather than a "whip antenna designed for the 10m band", then
you should have good reception in the 80m to 20m range even if the antenna
isn't well matched.
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WB2WIK
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« Reply #8 on: March 08, 2013, 01:36:54 PM »

I don't think anyone else mentioned it also depends on exactly what the "old but good radio" is.

Many modern HF transceivers intentionally reduce sensitivity in the AM broadcast band to help reduce interference to 160m amateur band reception caused by powerful AM stations.

In fact, "most" of them do.  My rigs are mostly 20 dB "down" in sensitivity below 1.8 MHz, by design.

Also, a 10m whip (say a 96" long 1/4-wave whip) is a terrible match for an amateur radio receiver which is optimized for 50 Ohm antenna systems; an AM broadcast receiver with a "loopstick" antenna or similar is way better matched by design, even though the antenna is very small.
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W5WSS
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« Reply #9 on: March 08, 2013, 07:32:27 PM »

I have a Hustler MO-1 mast with all the individual coils to choose one for the band of interest. It's installed vertically and located indoors next to an interior wall about 15 ft of base height above poor earth conductivity etc.. The antenna fits the space from 10m to 20m for the lower bands. I can easily add a longer wire attaching it at the tip of the whip and routing it along the ceiling. The structure is wood frame but I guess there is exterior metal meshing for the plaster etc. everywhere around the exterior walls so the performance is being evaluated.

The vertical system consists of a complete set of tuned horizontal radials 2 per band from 10m-40m.
They are routed and centered relative to the vertical and feed point, evenly around the base board.
 The system tuned and quieted down with the addition of the horizontal elevated tuned and ground isolated radial sets.

This is intended to be a DX sensitive system as quarter wave can be.

I am able to hear and work stations otherwise impossible when compared simultaneously via A/B rapid switching to any indoor horizontal full size dipoles or loops that work very well high angle.

Try the indoor vertical with radials keep the transmit power at safe levels.

I am having good success with the combination of the two.

73




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WD4ELG
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« Reply #10 on: March 08, 2013, 07:34:34 PM »

JT65 on FT817 to a Miracle whip. 5 watts, not too hard to make a qso on 20 meters. I also had a CW qso on 30 cw, but qsb killed it.  Realistically, I don't expect much except for digital modes. SSB?  Forget it.  CW? Maybe on the higher bands.
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W5DXP
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« Reply #11 on: March 09, 2013, 08:35:50 AM »

If receiver sensitivity is the problem, an antenna tuner will boost the signal to the receiver. Unfortunately, it boosts the received noise by the same amount.

What are you using for a counterpoise for your whip?
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
K0OD
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Posts: 2558




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« Reply #12 on: March 09, 2013, 10:55:57 AM »

"What are you using for a counterpoise for your whip?" Yep, without that you might as well just use a length of cheap hookup wire, which might be fine for reception.

--
I tried the utter opposite approach to operating when I lived in the two story apartment. No QRP for me! Young, foolish and gung ho for DX I built a Heath SB-220. Dumped 1500 red hot Watts into the dipole on my balcony.

Dumb! Lights in the entire building dimmed when I keyed. Soon I was getting calls from the complex manager several buildings away about her new TV problems.
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