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Receiver working, sensitivity issues?


 

Hi, I am able to rx a few stations locally
Got to hear someone speaking from about 1400km away on 20 Meters.

However, the issue is the signals that I get are pretty weak. I am using a homemade 1meter diameter loop antenna without any BalUn or tuning capacitor.

Currently, I don't have any VNA to gauge the antenna response. (Looking forward to getting Nano VNA...any other recommendations would do)

At times the signals are rising in amplitude and falling in amplitude (?fading?)

I live on the ground floor of an 8floored building. The terrace is about 100-120Feet from my house. The building is surrounded by other buildings, however ever there is a visible sky.

I took my rig to the terrace and still the signals are weak! I could hear someone from Mumbai locally talking to someone else. Only one-sided communication was rxd ie the local ham speaking which itself was weak.....

Tried adjusting the VFO and BFO....the audio was clear but weak.... a lot of static noise.



What would be the best way to go about understanding what is wrong here and where should I start from?

rgds
Simran


Will B
 

Hi Simran! :-)

I have used loop antennas in the past, and if they aren't tuned well, they can be almost deaf.? If you can, try to get a tuning capacitor for the loop as soon as you can, which will help dramatically, at least in my own experiences.?

I have seen that people use a large value variable capacitor (200 or more pF) for 'rough' tuning, then also use a smaller value variable cap for fine-tuning.? Variable capacitors are not easy to find, but they are out there.? I often have to purchase old stereos, clock radios and the like to grab the variable caps from them.? I've only used one (large value) variable capacitor for my loops, and that was just fine for good receiving.? Just know that they are very touchy!

I'm sure more experienced / more intelligent folks will answer here, but those are my meager suggestions.

Blessings and 73!

Will B
AF7EC


 

Hello Will, thanks for the reply.
The loop that I made was by taking a string...hooking it to one of the leg of a chair... measuring 1Meter length and exactly placing a marker pen at the end of 1 meter.
Drew an arc over a wooden plank and managed to make a guide along the arc created. An aluminum pipe of 10mm was put via the guide and the hollow aluminum tube was rolled.

I will look out for a capacitor. I would also like to experiment with other kinds of antenna which i can place on the ground floor itself.

Let me know what worked best for you guys.

rgds
Simran


 

Simran

You can make your own variable capacitor from insulators and conductors.
Formulas are available for calculating the amount of capacitance from size
of plates and dielectric constant of the insulators.




Capacitor insulators can be made from thin plastic from the sides of 2 liter
soft drink bottles.?

Capacitor plates can be made from almost any conductive metal, but copper
sheet or aluminium sheet would be best.

The layout can have the plates rotate from the center (half circle plates) or
by having them rotate from one corner (rectangular plates).

Arv
_-_





On Thu, Jun 3, 2021 at 3:30 PM <arorasimran@...> wrote:
Hello Will, thanks for the reply.
The loop that I made was by taking a string...hooking it to one of the leg of a chair... measuring 1Meter length and exactly placing a marker pen at the end of 1 meter.
Drew an arc over a wooden plank and managed to make a guide along the arc created. An aluminum pipe of 10mm was put via the guide and the hollow aluminum tube was rolled.

I will look out for a capacitor. I would also like to experiment with other kinds of antenna which i can place on the ground floor itself.

Let me know what worked best for you guys.

rgds
Simran


 

Hello Arv thanks for the reply. I will certainly try to first procure the caps and build aswell once the setup is done with formally mfg caps.

There is this group on FaceBook called as Minimalist QRP? and a poster named Billy Cheung has done phenomenal work by 3d Printing Capacitors.

It's very inspirational too.

Thanks for the links.

In the meanwhile, What are you guys suggesting when it comes to inverted V Antenna. There is a mango tree right in front of my house. I can surely do something with it.
Any leads with plans w.r.t inverted V would be of great help!

Thanks
Rgds
Simran
P.S My call sign is yet to be assigned to me... things are going at a snails pace with the government department. :(

?

?

?

?


 








On Thu, Jun 3, 2021 at 4:14 PM <arorasimran@...> wrote:
Hello Arv thanks for the reply. I will certainly try to first procure the caps and build aswell once the setup is done with formally mfg caps.

There is this group on FaceBook called as Minimalist QRP? and a poster named Billy Cheung has done phenomenal work by 3d Printing Capacitors.

It's very inspirational too.

Thanks for the links.

In the meanwhile, What are you guys suggesting when it comes to inverted V Antenna. There is a mango tree right in front of my house. I can surely do something with it.
Any leads with plans w.r.t inverted V would be of great help!

Thanks
Rgds
Simran
P.S My call sign is yet to be assigned to me... things are going at a snails pace with the government department. :(

?

?

?

?


 

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You might look at the SOTABeams web site.? They often use an EFHW.

Gerry

Sent by the Thunderbird

On 2021-06-03 5:14 p.m., arorasimran@... wrote:

Hello Arv thanks for the reply. I will certainly try to first procure the caps and build aswell once the setup is done with formally mfg caps.

There is this group on FaceBook called as Minimalist QRP? and a poster named Billy Cheung has done phenomenal work by 3d Printing Capacitors.

It's very inspirational too.

Thanks for the links.

In the meanwhile, What are you guys suggesting when it comes to inverted V Antenna. There is a mango tree right in front of my house. I can surely do something with it.
Any leads with plans w.r.t inverted V would be of great help!

Thanks
Rgds
Simran
P.S My call sign is yet to be assigned to me... things are going at a snails pace with the government department. :(

?

?

?

?


 

Simran

For receive try stretching out 8m or more of wire. The ubitx was optimized? for full sized antennas, but 8m or more should bring some signals.?

Patiently learn about ham radio antennas. To get RF across coax with minimum loss, the antenna needs to be nearly matched. The EFHW was mentioned, it uses a special network to feed it at one end. Read resources on the web and watch video on basic antenna theory.?

Maybe your nation is very much still in pandemic, use the time to learn. Meanwhile use whatever wire you have to hopefully grab some signals.? Use headphones then the signals should be louder.?

Glad to have you joining global ham radio.?

Curt wb8yyy


 

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I’m actually amazed that you are doing as well as you are. ? There is a concept called “aperture”that relates to the volume of space from which a given antenna extracts signal

If you have more aperture, you have more signal captured. A 1 m loop I think will have a very small aperture

Luckily at home frequencies, we work with signals that are not at the very bottom of the capabilities of most receivers. That’s because the background noise just from the galaxies lightning storms etc., is considerable.

However you face the additional hindrance that you have buildings around you and those absorb power from incoming signals that have to pass through them based on their geometry. ?If the only clear sky you can see is directly above you, then only signals that come in from that angle will be unhindered

Wise person has said that the best antenna is to get “as much wire as you can, as high as you can, and then match to whatever its impedance is.”

I thought that was worth remembering!
It might give you further ideas.


Gordon Kx4z?

On Jun 3, 2021, at 21:33, Curt via groups.io <wb8yyy@...> wrote:

?Simran

For receive try stretching out 8m or more of wire. The ubitx was optimized? for full sized antennas, but 8m or more should bring some signals.?

Patiently learn about ham radio antennas. To get RF across coax with minimum loss, the antenna needs to be nearly matched. The EFHW was mentioned, it uses a special network to feed it at one end. Read resources on the web and watch video on basic antenna theory.?

Maybe your nation is very much still in pandemic, use the time to learn. Meanwhile use whatever wire you have to hopefully grab some signals.? Use headphones then the signals should be louder.?

Glad to have you joining global ham radio.?

Curt wb8yyy


 

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hight is might ... and an elmer once said to me if you can not make it high then make it long :-)

dg9bfc sigi

(allday aerial is a 170m lopp 10m agl)

Am 04.06.2021 um 03:56 schrieb Gordon Gibby:

I’m actually amazed that you are doing as well as you are. ? There is a concept called “aperture”that relates to the volume of space from which a given antenna extracts signal

If you have more aperture, you have more signal captured. A 1 m loop I think will have a very small aperture

Luckily at home frequencies, we work with signals that are not at the very bottom of the capabilities of most receivers. That’s because the background noise just from the galaxies lightning storms etc., is considerable.

However you face the additional hindrance that you have buildings around you and those absorb power from incoming signals that have to pass through them based on their geometry. ?If the only clear sky you can see is directly above you, then only signals that come in from that angle will be unhindered

Wise person has said that the best antenna is to get “as much wire as you can, as high as you can, and then match to whatever its impedance is.”

I thought that was worth remembering!
It might give you further ideas.


Gordon Kx4z?

On Jun 3, 2021, at 21:33, Curt via groups.io <wb8yyy@...> wrote:

?Simran

For receive try stretching out 8m or more of wire. The ubitx was optimized? for full sized antennas, but 8m or more should bring some signals.?

Patiently learn about ham radio antennas. To get RF across coax with minimum loss, the antenna needs to be nearly matched. The EFHW was mentioned, it uses a special network to feed it at one end. Read resources on the web and watch video on basic antenna theory.?

Maybe your nation is very much still in pandemic, use the time to learn. Meanwhile use whatever wire you have to hopefully grab some signals.? Use headphones then the signals should be louder.?

Glad to have you joining global ham radio.?

Curt wb8yyy


 

Wire, yes, and don't be picky about it.? Old CRT TVs or monitors have deflection coils with lots of thin wire that is free and nearly invisible.? Push it through the screen in your window and far out into the world.? Then scrape the end of it (it's covered in enamel) and hook it up to one terminal of your antenna connector.? Hook up the other terminal to a ground, or just more wire, going somewhere else.? Try different stuff.? Did this as a kid, still doing now, and even transmitting on it using a cheap antenna tuner.


 

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my 170m loop is made from 3mm antenna wire ... a thin wire from a tvset wont work

dg9bfc sigi

Am 04.06.2021 um 04:32 schrieb masch57:

Wire, yes, and don't be picky about it.? Old CRT TVs or monitors have deflection coils with lots of thin wire that is free and nearly invisible.? Push it through the screen in your window and far out into the world.? Then scrape the end of it (it's covered in enamel) and hook it up to one terminal of your antenna connector.? Hook up the other terminal to a ground, or just more wire, going somewhere else.? Try different stuff.? Did this as a kid, still doing now, and even transmitting on it using a cheap antenna tuner.


 

I think we are addressing multiple topics now. The paradigm of the small loop versus a longer length of wire as a receive only antenna. For the latter wire diameter less critical.??

Simian don't be discouraged as you learn and explore. I hope you are receiving with your ubitx soon. A longer wire for receiving is easier to get working first, while you continue to consider a loop. I have qso with a few folk who used a small loop, but they always have substantial conductor and a sharp tuning network.?

Curt