R7100 antenna recommendations

[shortride]

As a novice I'm not sure which antenna would be the best choice for my newly inherited Icom IC-R7100 receiver. I like to listen to all of the bands and would like an antenna that would best accomplish that if possible. I'm sure everyone has their favorite antenna but I would like to hear from you guys that have been around the longest with the most experience.

[W2NJS]

Not enough data in your post to furnish a competent answer. Do you wish to listen to HF, VHF, UHF, etc.? For HF a multiband dipole would be ideal. Perhaps at this point the printed or online catalogs from the ham stores such as HRO or AES would give you the best view of what's currently available.

[W9BU]

The frequency range of the IC-R7100 is 25-2000 MHz. Very few antennas cover that entire band with consistent effectiveness across that entire band. Diamond now has an "ultra-wideband" discone antenna, the D3000N, that they claim covers 25-3000 MHz, but it has essentially no gain. Their older discone, the D130J, covers 25-1300 MHz. There may be other discones out there worth considering--they will have an omni-directional pattern. You may also want to consider a log periodic antenna for the VHF-UHF bands as they will have some directivity.

[shortride]

Originally Posted by W9RXR

The frequency range of the IC-R7100 is 25-2000 MHz. Very few antennas cover that entire band with consistent effectiveness across that entire band. Diamond now has an "ultra-wideband" discone antenna, the D3000N, that they claim covers 25-3000 MHz, but it has essentially no gain. Their older discone, the D130J, covers 25-1300 MHz. There may be other discones out there worth considering--they will have an omni-directional pattern. You may also want to consider a log periodic antenna for the VHF-UHF bands as they will have some directivity.

If I understand what I'm reading isn't an antenna like the D3000N actually two antennas in one.

Originally Posted by W2NJS

Not enough data in your post to furnish a competent answer. Do you wish to listen to HF, VHF, UHF, etc.? For HF a multiband dipole would be ideal. Perhaps at this point the printed or online catalogs from the ham stores such as HRO or AES would give you the best view of what's currently available.

I would really like to listen to HF, VHF and UHF if that's possible. I can put up a wire antenna if I need to.

[ka3jjz]

The R7100, as noted earlier, only goes down to 25 Mhz. That's a very small toehold in the HF world - and there really isn't too much, apart from hams, CB and a few IFBs in this range. I don't know of many broadcasters in the 25.5 - 26.1 Mhz range - although it's the wrong time of the year for it, at least for us in the Northern Hemisphere...

Mike

[W9BU]

Originally Posted by shortride

If I understand what I'm reading isn't an antenna like the D3000N actually two antennas in one.

No, the disc and the cone are both elements of the same antenna.

The lower frequency of discone's range is determined by the length of the cone elements. That length then determines the diameter of the disc element. The nature of the discone is such that the high end of their range is roughly 10 times the low end of their range.

Several discone manufacturers, Diamond included, take the traditional discone design and add a center vertical element whose purpose is to lengthen the antenna to make it work at even lower frequencies than the basic design would allow.

[shortride]

Originally Posted by W9RXR

No, the disc and the cone are both elements of the same antenna.

The lower frequency of discone's range is determined by the length of the cone elements. That length then determines the diameter of the disc element. The nature of the discone is such that the high end of their range is roughly 10 times the low end of their range.

Several discone manufacturers, Diamond included, take the traditional discone design and add a center vertical element whose purpose is to lengthen the antenna to make it work at even lower frequencies than the basic design would allow.

Thanks, I appreciate the information.

[prcguy]

For most scanner type Discones the freq range of the Discone part is about 100MHz on the low end to about 800Mhz on the high end and they work very well from about 100Mhz to maybe 500MHz before the radiation pattern starts to point up from the horizon, so they are not that good on 800MHz. The whip on most of these is tuned sharply to 50Mhz to extend the low end but its not very good in the 25 to 45Mhz range or in the 55 to maybe 90Mhz range.

I have an IC-7100 buried somewhere in the garage, I should probably see if it still works.
prcguy
prcguy

[carmelof]

Hi i use an Icom-AH7000 discone works excellent on all bands its been replaceby the AH8000 and this is a short video of my Icom-R7100 monitoring the airbands location melbourne radar controller in australia distance is around 80 km antenna is 10 metres high with Belden-9913 coax cable..

Airbands - YouTube

Regards Lino..

[shortride]

Anyone know the diameter of the short mast that the D3000N elements mount on? I've looked at several website information and they don't mention the size. I'm trying to plan some sort of mounting apparatus to attach the antenna to a utility pole. 1-1/2" to 1-3/4" maybe?

[Squad10]

http://www.diamondantenna.net/pdfdocs/D3000N.pdf

Applicable mast diameter (0.98" to 2.05")

[shortride]

Originally Posted by Squad10

http://www.diamondantenna.net/pdfdocs/D3000N.pdf

Applicable mast diameter (0.98" to 2.05")

Thanks! That helped a lot.

[k3cfc]

Originally Posted by shortride

As a novice I'm not sure which antenna would be the best choice for my newly inherited Icom IC-R7100 receiver. I like to listen to all of the bands and would like an antenna that would best accomplish that if possible. I'm sure everyone has their favorite antenna but I would like to hear from you guys that have been around the longest with the most experience.

You should try to get an hf ham radio even if it won't transmit all you want to do is listen anyway. then maybe you will look into getting a ticket and get into some fun. you could make a carolina windom antenna and listen to the world.

K3CFC

[shortride]

Originally Posted by k3cfc

You should try to get an HF ham radio even if it won't transmit all you want to do is listen anyway. Then maybe you will look into getting a ticket and get into some fun. You could make a Carolina Windom antenna and listen to the world.

K3CFC

A local amateur radio operator friend has been trying to talk me into getting a ticket for years. It would be expensive for me. I have a Grundig Sat 8 SW radio now and don't use it much. This Icom IC-R7100 receive was an inheritance and I thought it would be fun but it turning out to be a bit more difficult to learn than what I was expecting. Thanks for the suggestion.

[shortride]

I received the D3000N antenna and the 100' roll of coax yesterday. Like a dummy I ordered RU-213-U coax and it is way bigger and heavier than what I needed. I should have ordered RG-8X.

[W9BU]

Keep in mind that the attenuation in coaxial cable increases with the length of the cable. Additionally, different types of coax have different attenuation ratings. Generally, RG-213 has a better attenuation rating (that is, less attenuation) than RG-8X. Over a length of 100 feet, the difference in attenuation between those two types can be significant.

Coax attenuation also increases with frequency. In other words, a 450 MHz signal will have a harder time getting through a length of coax than a 150 MHz signal. So, given the improvement in attenuation of RG-213 over RG-8X and the 100 foot length that you bought, the RG-213 was probably a better decision on your part.

[shortride]

Originally Posted by W9RXR

Keep in mind that the attenuation in coaxial cable increases with the length of the cable. Additionally, different types of coax have different attenuation ratings. Generally, RG-213 has a better attenuation rating (that is, less attenuation) than RG-8X. Over a length of 100 feet, the difference in attenuation between those two types can be significant.

Coax attenuation also increases with frequency. In other words, a 450 MHz signal will have a harder time getting through a length of coax than a 150 MHz signal. So, given the improvement in attenuation of RG-213 over RG-8X and the 100 foot length that you bought, the RG-213 was probably a better decision on your part.

Does the 3’ incremental length of coax apply for a receiver only as it does with a transceiver? I was wondering if I have a fixed antenna height and distance from the antenna to the receiver, can I cut off any excess coax?

[Squad10]

3' incremental length does not apply.

Yes, you can cut off the excess coax off. I always leave about an extra 15 feet in my monitoring room in case I want to change my receiver's location.

Be certain to get the coax connectors put on the coax so the coax center conductor and shield do not short.

[W9BU]

Originally Posted by shortride

Does the 3’ incremental length of coax apply for a receiver only as it does with a transceiver?

Yes. The attenuation in an RF feedline applies to both received and transmitted signals. The attenuation is usually quoted in terms of dB of attenuation or loss per 100 feet. So, 3 feet of a a feedline rated at 6 dB/100 feet attenuation would have 0.18 dB of attenuation.

Originally Posted by shortride

I was wondering if I have a fixed antenna height and distance from the antenna to the receiver, can I cut off any excess coax?

Yes, you can shorten the coax to suit your installation. But, make darn sure you know how to properly install a coax connector on the cut end.

[k9rzz]

I would go with the discone for general listening, then if you got hot into monitoring one service, put up a special antenna for that. For example a 6 meter ham beam, 2 meter ham, or FM broadcast antenna. I even built up a stack of home brew beams for the NOAA weather stations on 162mhz. KILLER! :^) No reason you couldn't do the same for rail, air, lowband VHF, satellite, what have you. I also swapped out the 10.7mhz ceramic IF filter (~320khz) for a narrower Murata 110khz job and hooked it up to some Weingard 6065p antennas on the roof. Again, KILLER! The R7100 makes a nice DX rig for FM broadcast if you fix the wide bandwidth that it ships with. Enjoy!